


Doom and Demon slayers

by Anakin80042



Category: Doom (Video Games), 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Kimetsu no Yaiba (Manga)
Genre: Action/Adventure, Blood and Injury, Crossover, Demons, Fights, Gen
Language: English
Status: In-Progress
Published: 2020-03-19
Updated: 2020-08-09
Packaged: 2021-03-01 02:08:15
Rating: Teen And Up Audiences
Warnings: Graphic Depictions Of Violence
Chapters: 7
Words: 28,193
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23217511
Author URL: https://archiveofourown.org/users/Anakin80042/pseuds/Anakin80042
Summary: Where there are Demons, there be Doom: The Doom Slayer is unwillingly sent to a foreign world festered with foreign demonic forces. Guided only by his rage and a shotgun, The Doom Slayer is quick to rip and tear his way through this world's demon hierarchy. With new responsibilities and challenges, however, The Doom Slayer may need more than bullets and BFG's to raze hell.Or just more bullets.Author's side note: "The only promise I can make about this story is that Shinobu will get a chainsaw."
Comments: 45
Kudos: 169





	1. Limbo of the Slayer

**Author's Note:**

> Author’s note:  
>  I actually haven’t played DOOM before, but I’m interested in both the lore and the Doomguy (AKA Doom Slayer) himself. Whatsmore, I thought it would be interesting to see If DOOM and Kimetsu No Yaiba (AKA Demon Slayer) mixed in this sort of way, since they both have the same goal of eradicating demons.  
> I took some creative liberties for this story, and I hope that such liberties do not taint the reputation of either franchises.  
> Also, the Doomslayer’s armor design will look similar to DOOM Eternal’s suit, eventually. He starts out like DOOM 2016, as the story continues after the invasion on Mars.  
> Other than that, please enjoy:

**Summary for the Chapter:**

> Where there are Demons, there be Doom: The Doom Slayer is unwillingly sent to a foreign world festered with foreign demonic forces. Guided only by his rage and a shotgun, The Doom Slayer is quick to rip and tear his way through this world's demon hierarchy. With new responsibilities and challenges, however, The Doom Slayer may need more than bullets and BFG's to raze hell.  
> Or just more bullets.
> 
> Author's side note: "The only promise I can make about this story is that Shinobu will get a chainsaw."

**Notes for the Chapter:**

> Author’s note:  
> I actually haven’t played DOOM before, but I’m interested in both the lore and the Doomguy (AKA Doom Slayer) himself. Whatsmore, I thought it would be interesting to see If DOOM and Kimetsu No Yaiba (AKA Demon Slayer) mixed in this sort of way, since they both have the same goal of eradicating demons.  
> I took some creative liberties for this story, and I hope that such liberties do not taint the reputation of either franchises.  
> Also, the Doomslayer’s armor design will look similar to DOOM Eternal’s suit, eventually. He starts out like DOOM 2016, as this takes place directly after it's end.  
> EDIT: Fixed some grammar errors with the chapter.  
> Other than that, please enjoy:

/////////////////////////////////////////////////////////////////////////////////////////////////

_U.A.C – Mars - Lazarus Lab, Site A – Main Computer_

_///////////////////////////////////////////////////////////////////////////////////////////////_

_[RUN LAB DIAGNOSTICS]_

_[enter device]_

_[device:_ _Tether_ _]_

_Tether device used to transport paraphernalia between different dimensions. Power levels 100%. Structure integrity is 100%._

_[LOG]_

_Tether was used CLASSIFIED/CLASSIFIED/CLASSIFIED ago on_ [REDACTED].

_[ACCESS SECURITY SYSTEMS]_

_[CLASSIFIED]_

_[OTHER]_

_[LOGIN]_

_[Identification required. Please enter the password and scan your card.]_

_[PASSWORD: ErawtfosDI1993]_

_[SCANNING]_

_[SCANNING]_

_[SCANNING]_

_[IDENTITY CONFIRMED: Welcome, Samuel Hayden.]_

_/////////////////////////////////////////////////////////_

_[RUN LAB DIAGNOSTICS]_

_[ACCESS SECURITY SYSTEMS]_

_[DOWNLOAD]_

_[Download files]_

_[Downloading coordinates]_

_[Download complete]_

_[OTHER]_

_[ACTIVATE TETHER]_

_[CHOOSE LOCATION]_

_[Input coordinates:]_

_[Earth]_

_[Hell]_

_[Project Phineas Passage]_

_[location: secured]_

_[Paraphernalia: confirmed]_

_[Energy levels: sufficient]_

_[Are you sure you wish to proceed? This action cannot be undone]_

**_[_** ** _YES]_** _[NO]_

_[Confirmed. Tether activating in,]_

_[T-5]_

_[T-4]_

_[T-3]_

_[T-2]_

_[T-1]_

_[Tether activated.]_

_/////////////////////////////////////////////////////////////////////////////////////////////////_

Blue tendrils of light rocked the cavern. In a blast of violent energy, a human body exploded into reality, dropping to the ground in a relatively unimpressive fashion. Water dribbled onto his head; trickled down his naked physique. Brushing the cave dust off of him, he stood to attention.

In front of him was his Praetor armor: An imposing green suit. Otherwise, he was alone in the misshapen cave, sealed from the outside world by a steel door.

Upon inspection of his armor, he was dismayed to find it still… “modified,” the U.A.C Tether device still welded onto it’s elbow plate. Additionally, a holster for a U.A.C EMG pistol was strapped to its right hip. No matter. He’d done more with much less. He grabbed the verdant armor once more.

Visions pounded his head. Of Mars. Of the hordes of hell. Of Olivia Pierce. Of the Crucible. The U.A.C. Samuel Hayden.

His fists clenched as he remembered Samuel Hayden, how he had stolen the Crucible and used the tether system to drag him away like a bad dog. He was probably experimenting with the crucible now, blind to the untameable nature of hell and it’s residents.

He ripped the elbow plate out – the tether with it – and smashed it into the wall. Neither broke, so he kicked it deeper into the cavern. His right elbow was exposed, but he wasn’t the U.A.C's dog anymore.

He kicked down the door, expecting blood clouds dripping over umbral plains. He was welcomed, instead, by a calm forest; brushed in moonlight, speckled in gentle strokes of pine trees. The chitter of fireflies and gentler things shadowed the thumps of his wary footsteps. It looked like Earth, but the dimension veteran knew the difference. He fired a warning shot into the air.

The bushes rustled. Suddenly, a snow-white rabbit hopped into the clearing, pink nose twitching in the air. It didn’t run when he approached it. Quite the opposite: It happily bounced to him. He held out his hand, and the small fur ball happily complied.

It was…cute.

\---------------------

“Man, this sucks,” he grumbled.

He hadn’t seen another human in days. People used to travel this route all the time. Now he was lucky if he could find any footprints.

“What a pain,” he groaned. “Maybe I scared them all off again? Ugh, I bet there’s another demon feasting on some plump humans right about now…” he hungrily licked his lips. “What a pain…” He didn’t want to go another night empty-handed. His nose - many times more potent than a human’s own - furiously twitched. 

He gagged, as if someone had shoved two skunks up his nose. _What the hell? I thought I cleared this area out!_ He growled as he hunted for the source of this poignant smell.

As a rule of… that man… demons weren’t allowed to work together unless given special permission. Because of that, stronger demons always pushed weaker ones like him around. It had taken him years to secure this spot. It was his and his alone. _No one_ was going to take it from him.

Besides, what’s the worst that could happen? Demons couldn’t kill demons. His life was assured. _Unless it’s one of those Twelve Demon Moons. They could seriously mess me up_ he growled.

The horrible smell, akin to a pile of rotting corpses, slowly grew stronger as he approached the intruder. He noticed something unusual about it. Unlike normal demons, this one had an electric sizzle to it, like a soda drink ( _What’s a soda?_ He briefly wondered). The stench also had a texture to it, similar to dry paint. Finally, he found the demon.

The odd demon marched through the forest. Shoulders high, hands rested on a blue gun holstered at his hip, he was washed in a seaweed-paint job. The demon’s armor appeared to be the source of the smell. However, he could see that there was an ordinary man underneath. Now he was confused. It was obvious he wasn’t normal human prey, but was he really a demon? If anything was out of place, it would be the white rabbit that rested on his shoulder. Asleep, the creature used its ears as personal blankets against the cold night.

_Maybe it’s a new trick by the Demon Slayer Corps to scare weaker demons,_ his mouth wavered, _Not that I’d be dumb enough to fall for that. I can still smell human flesh! It’s delicious!_ His demon instincts kicked in. Ignoring the horrible odor, this human was a seaweed-wrapped dumpling.

Serpent avarice blinded him. He viciously pounced on his prey.

Faster than the blink of an eye, the man grabbed his face and pounded him into the dirt, crushing his skull like a hollow log. Without any reaction of surprise or care, the man carried on. The white rabbit sleepily scratched its ears. The demon blinked (metaphorically), his inhuman brain trying to keep up with what had just happened. _Huh? H-how did he get me?_

As his head painfully sculpted itself back together, he growled. “Hey! What the hell are you doing on my turf?” The human stopped. “Yeah you! Whatever you are, get lost! this is my turf!” His hair tendrils flayed. His iron nails extended. “If you don’t, I’ll make sure you regret it!”

The man cracked his knuckles. The Demon grinned. He would die braver than most. “Time to pay!” He lunged at his prey.

Compared to humans, demons were undeniably superior. With unending regeneration, limitless stamina, demonic strength, and immortality, demons were easily capable of taking down hundreds of humans. One alone was nothing.

True there were those who had bested the odds, but they were a finite, extinguishable number. Demons were immortal. Tireless. Numerous.

Demons were superior.

Yet, as he lashed out once again, he finally realized why the smell was so thick. It wasn’t a single smell, but rather the smell of thousands, millions of demons.

In that instant, he didn’t feel superior. He felt overwhelmed. He eyed the man’s exposed right and lunged; countered by a sudden grab around his throat. The green man viscerally tore his head off.

“You fool! I don’t need my body to attack!” His hair tendrils pierced the man’s helmet. They connected, but they failed to penetrate the verdant armor. He switched targets and attacked the sleeping rabbit instead. Inches away, he felt an immense pressure squeeze his skull. SQUISH, the man crushed his head whilst his headless body continued to ravage the intruder.

_Quick, powerful, and impervious to damage, but I'm certain now he is a human. He’ll eventually tire himself. When that time comes, he’ll pay for messing with me!_

\---------------------

Hours later, the cries of the demon were snuffed out by the prompt _CRACK_ of another femur. The demon – or what remained of him – tried to crawl away.

“Stop, stop!” he cried as the monster crushed his chest once again. “I’ll…I’ll tell you anything! Everything! I’ll tell you how to kill me if you stop it!”

The monster paused.

“l…look. I can tell you aren’t from around here. But to kill Demons like me you need to-um-to expose us to a full moon. The full moon! Only it’s bright light will disintegrate us into ash.” As he rambled on, the morning sun rose behind the monster. Distracted, the demon didn’t notice until the sunlight brushed his hair. The monster glared at the burning strand, tears and sweat pouring down his face.

“Oh, this? Yes, we’re also weak to the sun. Didn’t I tell you that? Now, please, let me go and-“ The monster tore off a chunk of his flesh and kicked the demon into the sun. His cries soon fell silent.

The constant movement of the night had made the rabbit uncomfortable, so he had nestled himself into a tidy corner near the fight. Yawning with the morning sun, It brushed itself awake and hopped to the Doom Slayer's side. Reluctant at first, The Doom Slayer held out his hand, and the rabbit happily returned to its rightful seat.

\---------------------

The Doom Slayer reached into his pants and pulled out a silver microchip. For a brief moment, he unclipped his helmet and inserted the chip into it.

PROGRAM INITIALIZING

PROCESSING, 50% complete

PROCESSING 99% complete

VEGA INITIALIZED.

VEGA’s program trickled through the Praetor’s systems. Once fully integrated into the suit, it accessed the last recorded memory prior to its mandatory shutdown, and continued.

“VEGA initialized,” the A.I announced. “Hello, Doom Slayer. It seems as if I am still operational. I thought that the destruction of my main core would render all my processes inert and inoperable. Did you backup my AI?”

Silence.

“I understand. I am surprised that the Praetor suit is advanced enough to run an A.I as sophisticated as myself.”

The Doom Slayer showed VEGA the chunk of flesh.

After a quick scan, VEGA said “These cells share a close connection to human cells, but a foreign object of some kind has corrupted them into something else. They are constantly dividing, though how it could do this without a connected intelligence is unknown. I cannot make any conclusions based on this small sample.”

Silence.

“Unfortunately, while advanced, the Praetor suit was not made for in-depth analysis. It is suited for the collection of it. Collect additional samples and I will record any new findings in your suit’s CODEX.”

The Doom Slayer burned the remaining flesh. Softly, he showed VEGA the rabbit.

“Scan complete. This is a rabbit – nothing unusual about it.” He gently placed the furry hitchhiker onto his shoulder, comforting it with a light pat. As the sun rose over the horizon, he continued his aimless march.

\---------------------

Giyu marched through town after town, barely stopping to eat, sleep, or rest. It had taken weeks to get here; it would be another day before he arrived at his destination and begin his mission. His thoughts, however, tired him more than the journey. He was well past self-preservation – years spent fighting demons had wrestled that away from him. Retribution concerned him instead. A week ago, a Kasugai crow had arrived at the Butterfly Estate with reports of a demon. The demon himself was an adult man with blood-red eyes and a mahogany suit, travelling at night on barren pathways. In his hand, he held what appeared to be an apple-colored skull. The message also came with a call for help. When reinforcements had arrived, half of the patrol had died, their corpses drained like dried prunes. The other half was wounded, initially. Shinobu was busy at the time, so she wasn’t there to witness the survivors become demons.

Giyu was sent to investigate.

He flashed his Nichirin sword, taking note of any imperfections in it’s edge. If the reports were true, and this really was the leader of the demons he was following, then he would have to give nothing less than his best. For all he had lost.

For Sabo.

In the distance, he saw a farmer arguing with someone. Their conversation steadily grew louder and brasher.

“Is that helmet of yours too thick? Like I said, you have to PAY for that!” The farmer yelled. “You can’t just barge in and take whatever you want!”

“Darling, please just let the man take it.” The farmer’s wife said. “He needs it for his little pet!” The rabbit beamed as the wife scratched his head.

“I can’t just give whatever we have to whomever passes by, whether they be cute or not. Now, if he pays for it, then I’ll gladly let him go.” The man tried to rip his sheets back from the stranger. Tried. He would’ve had better luck ripping them from a bear.

“Darling, look. maybe he’s new around here. Besides,“ she gestured to the bulging monstrosity that somehow still classified as a human elbow. “I don’t think we are in a position to argue.”

“Oh, OH. A scoundrel, are we? Trying to be a big boy?” The farmer rolled his sleeves. “C’mon then!” The strange man walked away. “Yeah, that’s right! Not so tough now are you?” He turned to his wife. “See? I’ve still got it. He’s leaving us alone.”

“With our belongings, dear.”

“But he’s leaving. And you say you regret marrying me.” The woman shook her head.

“Who was that man?” Giyu interrupted.

“Oh, him?” The farmer waved magnanimously, “Nothing you need to worry about. He’s just some scoundrel who took one of our good blankets. Barged right on in and took them – not without some trouble, of course.” He grinned. Behind him, his wife rolled her eyes.

_Strange,_ he glanced at the man walk away, wrapping his bunny in the stolen blanket. _Could he be Muzan in disguise? Is the armor his way of blocking out the sun? Or am I just paranoid?_ Giyu glanced at the old couple. He didn’t want to get them involved.

”Still,” the farmer continued, “Too bad he didn’t pay though.”

Giyu gave him a handful of coins. “This should cover for the blankets, yes?”

He frowned. “Are you a friend of his?” He leaned closer. “Do you know where he lives?” The old man whispered.

Giyu shook his head. The farmer thanked him, bid him a good day, and left with his wife. When they were out of sight, he followed the verdant man.

“Excuse me, I’d like to ask you a question,” He said.

The man kept walking.

Giyu blocked his path. “I don’t like to talk, so I’ll be brief,”

Briefly, the man pushed Giyu aside.

“Do you know of anyone crossing these roads at night? By themselves?” Giyu asked. The man didn’t stop, but he shook his head. _Of course. Muzan is a master at disguise. A stranger on the streets would be a cakewalk for him. And if this is him, then he'd never answer the question honestly._

“Are you native to Japan?”

The man ignored him.

“Where are you going?”

The man still ignored him.

Giyu tried one of Shinobu’s suggestions for situations like these: ‘small talk.’

“The weather’s good today” He said.

The man ignored him

“Is that thing in your pockets a gun?”

The man ignored him.

“Is that your rabbit?”

The man nodded.

“What’s it's name?”

Silence.

_I’ll try a more direct question._

“Are you aware of the Demons?” The man stopped suddenly. He turned and faced Giyu. Translucent lights flickered across his masked face. Giyu’s sword grip tightened. He’d struck a nerve, apparently.

“I am a part of the Demon slayer corps that acts independently from the government. I have a vital mission at hand, and I suspect you might be related to it.” Giyu said. “Do you know of a man with blood-red eyes? A man who goes by the name Muzan Kibutsuji?”

The man sized him up. His hair. His Haori. His sword. He grabbed the sword.

“That’s mine,” Giyu said simply.

Giyu dodged the stranger's sudden wild haymaker. He unsheathed his sword.

_Total Concentration Water Breathing 1st form: Water Surface Slash_

The water pillar swung his sword with the force of a tsunami. The stranger strafed to the side and shot Giyu in the leg. The bullet burned his skin, but he stayed steadfast. So the duel began.

Giyu was always ready for a fight, but was still surprised at the turn of events, especially how the stranger was fighting. The stranger didn’t use any Demon Blood Arts. He simply kept close to Giyu with inhuman speed and strength. However, he looked incomplete. His hands seemed uncomfortable around the strange gun he wielded. They were used to something bigger. Luckily, he didn't have that on him at the moment.

_Total Concentration Water breathing 8th_ _form: Waterfall Basin_

His sword rippled through the air with intense speed.

The stranger grabbed the blade by its side and raised his free-hand to crack Giyu’s arm. Giyu couldn’t pull the blade out of the iron grip. So he compromised. With a swift kick to the blade's side, he snapped the it in half. 

_Such efficiency_ He thought. He readied himself again. He would fight to the end, even with half a blade. But his enemy made no further attempts to fight. Instead, he examined the remaining end of the blade, then walked away.

Giyu read what was left of his sword, the kanji “KILL DEMONS'' now reduced to “DEMONS.” Overhead, a crow cawed as it landed next to Giyu. It pecked his head angrily. He sighed. 

\---------------------

“Upgrade complete, Makeshift, but it should serve its purpose.” VEGA concluded.

Using his remaining left arm plate, the Doom Slayer fashioned an arm-mounted piston. His fists clenched, and the Nichirin blade flashed out of the contraption. The words “KILL” shivered throughout the blade. He snapped it back in.

“It appears the language of this world is similar to the Japanese from Earth. As for the metal, it carries an energy signature similar to that of the sun. My conclusion is that this blade is designed to assist the ‘Demon slayers’ in killing demons. If I’m not mistaken, this wouldn’t be the first time you’ve run into another world that fought demons.”

Silence.

“I see you’re focused.” VEGA noted.

Silence, except for the slight but purposeful tilt of the Doom Slayer’s brow.

“There is no satellite technology here that I can connect to, so I will acquire it archaically. The top of this mountain should provide a good vantage point.”

“The rabbit will be fine in these cold temperatures,” VEGA added.

Soon, The Doom Slayer found himself trudging through the snow. Like umbrellas on the beach, the pine trees' shadows stretched under the midday sun. His rabbit relished the cold weather and joyously bounced ahead of him – sometimes out of sight. He always came bounding back.

“This would be the first time I’ve physically been on an Earth-like environment,” VEGA suddenly mentioned. “May I use your CODEX to log the environment?”

Silence.

“Thank you,” VEGA’s systems hummed as he scanned the generous forestry before him.

The Doom Slayer’s Praetor suit felt silly: the welcoming breeze of the mountain whispered nothing but peace and silence. No demons to tear. No unbreathable atmosphere to choke on. No war. The Doom Slayer kicked a lump of snow aside.

He preferred Mars.

“What is your plan, Doom Slayer?” VEGA said.

Silence.

“If you are looking for any familiar demons, I have not detected any signs of Argent energy. Argent Energy is crucial for dimensional tethering, so to have you transported to a place with none of it seems purposeful.” The Doom Slayer punched a hole through the nearest tree. Its cries as it fell echoed throughout the forest. “I apologize for not informing you of Hayden’s plans for the Crucible. I was forbidden from revealing it.”

"If it is any consolation, knowing Samuel Hayden, I doubt he tried to get rid of you. Statistically speaking, your available records against demons – documented from your crusade on Mars – show that you boast the highest efficiency and effective tactics in destroying demons out of any available army. Hayden likely sent you somewhere far away to keep you out of his work. You were originally his fail-safe against demonic invasions, and to send you without a way back would be a big risk if another Hell invasion ever happened. At the same time, Samuel Hayden is not known for avoiding big risks.”

“I do not have the appropriate information to determine why you are here. I can only infer that you being here is either a precaution, or a necessity.”

\---------------------

For a good hour, the Doom Slayer continued to trek up the mountain. It was near the end of that hour that he noticed the rabbit had stopped following him. He hesitated.

“Life signs detected, on your right.” VEGA helped. Following VEGA's guidance, as well as the little trails in the snow, he came into a clearing. There was the white rabbit, in the hands of a young girl.

“Hello, are you lost?” the girl asked. “What are you doing so far up the mountain little guy?” She smiled. The girl wore a pink haori. A small, sleeping child hung on her back. She tickled the rabbit. “We don't have enough space for a pet, but maybe I can take you back until I find you a new home. Does that sound good little fella?” The rabbit happily cheered in her hands.

He thought about leaving. Clearly this girl had plenty of love to share. He would be fine.

The rabbit thought otherwise.

Before the girl could carry it away, it bounced out of her hands and back to the Doom Slayer. It danced around his feet before The Doom Slayer picked it up again. The young girl watched with a mix of curiosity and confusion.

“Hello,” she said. “I didn’t notice you there. Are you all alone?”

Silence.

She smiled. “I’m guessing that rabbit belongs to you?”

The Doom Slayer nodded.

“Does it have a name?”

Silence.

“What do you mean it doesn’t have a name? Any cute pet needs a name,” The girl frowned, as if she had just read his mind. “How about…Daisy?”

The Doom Slayer shook his head.

“What about…Wisty? Like the Wisteria plant?”

“....”

“Okay. Nice to meet you mr…?”

“….”

“Sorry if I’m doing this thing all wrong,” she laughed. “I’m usually all alone in these mountains with my family. I don’t even know what’s beyond the nearest village. Are conversations usually this one-sided?”

Silence.

“Right. Let’s start from the beginning,” she held out her hand. “Hi there stranger. My name is Kamado Nezuko. What’s yours?”


	2. Discoveries Of the Slayer

**Notes for the Chapter:**

> Author’s note:  
> For anyone who isn’t aware, this fanfiction takes place after DOOM 2016. Furthermore, this fanfiction was released while Kimetsu No Yaiba was still ongoing. As a result, there may be plot inconsistencies.  
> I will also leave spoiler warnings for anyone who hasn’t caught up to Kimetsu No Yaiba yet, and specify which chapters/episodes they happen in. For instance:  
> Spoiler warning:  
> Spoilers for episode 1 of anime.  
> Please enjoy:

////////////////////////////////////////

As the snow drizzled on his face, Tanjro hopped back up the mountain, a fresh bag of food in hand. He had sold all of his charcoal for a generous price. He couldn’t wait to share the good news with his family. Everything was great. He was happy.

Suddenly, he smelled the thick, putrid scent of blood. His sensitive nose never lied. His hike broke into a sprint.

His breath swallowed; his eyes widened. His home, his _family,_ was a mess. Blood painted the walls. The eyes of his mother hung open in terror. His brother’s skin was snow cold. His sister’s pink kimono was stained red. He fell to his knees and cried.

“Tanjiro!” He cried.

“Tanjiro!” Someone cried.

“TANJIRO!” He jumped out of his bed – startled – and headbutted his younger brother. The latter stumbled onto his back.

“Ah! Takeo! Sorry!” He apologized.

“I’m fine,” Takeo groaned. “You were shaking. A lot. I thought you had a fever. Are you okay?”

Tanjiro wiped the sweat off of his face. “It was just a dream.”

“A dream about what?” Takeo asked excitedly.

“It was…” He thought for a moment. “It was about a really nice picnic.” His skin crawled at the lie.

Takeo noticed. “Liar! What was it really like? Was there blood? Guts? Did someone explode like this?” His brother feigned an expression of utter horror as a bundle of invisible guts gushed out of his stomach. He dramatically cried as his body tumbled to the floor. Dead silence, except for a small grin stretching across his face.

“You’re too young to think about stuff like that. Where did you get such ideas?” Tanjiro gently scowled as he got dressed.

“Are you going to go to town today?” Takeo asked.

“I was going to, but I think I’ll just stay here instead. We have enough food and money.”

“So, you’ll help me chop the wood, right?” He asked.

“Right.” Tanjiro grinned.

“I’ll get the axe!” Takeo whooped as he flew out of sight. “Oh! I forgot to mention!” He hastily added. ”Nezuko found a stranger and now he’s hanging out with us!”

The smell of blood and death choked Tanjiro’s awakened nose. He threw on his clothes and followed the horrible smell emanating from the kitchen. Thoughts of his family and knives trailed Tanjiro as he threw open the doors...

To find Routa shoving a spoonful of food into the stranger’s helmet.

“C’mon eat Mr. Stranger,” He chanted. The stranger gently swatted the baby hand away, but Routa remained steadfast. The spoon-feeding continued.

Nezuko and his mother entered the kitchen, respectively holding a white rabbit and some lettuce.

“Oh, Tanjiro, you’re awake.” Nezuko said. In her hands, the little rabbit squeaked with delight. “You seem very energetic today.”

“Did something happen while I was asleep?”

“Well, I was on my morning walk with Routa – you know how he loves those – and I met Kame and his little friend.” The rabbit purred as Nezuko massaged the perfect spot. 

“Kame?”

“Yes. That’s the name I gave him.”

“Why would you give him a name?”

“Ask him.” Nezuko pointed at the stranger.

Silence. Routa dropped the spoon and climbed on top of the stranger’s head.

“Kame doesn’t talk much. Anyway, I met him during my walk. As we 'talked', Routa woke up and wanted to play with Kame. One thing led to another and - well - look!” Routa expertly played the drums on the stranger’s head. “Routa no!” Nezuko laughed.

Their mother softly scowled as she pulled Routa off of Kame. “Now now Routa, it’s not polite to hit guests. Even if they are strangers, you must treat them as if they were your own family.” With the thoughtfulness of a toddler, Routa pouted as he stretched for Kame's helmet.

Kame reached into his pocket and gave Routa a toy-sized model of Kame himself: It had moveable arms, legs, and everything a toddler could want. Routa’s eyes sparkled as the toy played a hard guitar riff. “Gimme gimme!” He happily accepted the exchange and ran away with the toy, banging it on the head. 

His mother couldn’t resist laughing. “Oh my. He hasn’t been this happy in a while – not since Tanjuro’s death.” Her heart ached from the memory. She wiped the happy tears from her eyes. “It really is a special day today.”

“I hope you aren’t going down to town today Tanjiro. It’s not safe.” She said to him.

“Nope. We have enough food for now.”

“More than enough.” She gave Kame his rabbit and the lettuce. “Here. Free of charge. Please stay safe.”

“He’s leaving already?” Nezuko said.

“Nezuko, can’t you see? He’s a soldier: his home is where his duty lies.” She bowed. “You’re welcome here any time.”

Kame promptly left, sharing no salutations or gestures of gladness.

“He didn’t even wave goodbye,” Nezuko mused as she watched the stranger travel up the mountain. “I wonder where he’s planning on going. There isn’t anything special at the top.” Next to her, Tanjiro breathed a sigh of relief. “What is it?”

“I was worried there for a second.”

“You’re always worried Tanjiro. Have you seen his muscles? I’m sure he’ll be fine.”

He shook his head. “I was worried about what he would do to all of you. I could smell this thick scent of blood off of him.”

“He _is_ a soldier.” Nezuko reasoned.

“Maybe,” _But what kind of soldier wears armor like that? And what army does he belong to?_ Tanjiro didn’t have the answers, but now he knew his family was safe. The nightmare was no more real than any other dream. He relaxed, deciding to just enjoy the rest of the day.

////////////////////////////////////////

Kame passed by Takeo. The boy panted as he messily chopped the first log of the day. “Ugh. I’ve got to be more firm…” He muttered.

Kame picked up several of the logs. With his bare hands, he tore each of the logs in half and left. Takeo’s jaw dropped.

“WHAT THE FUCKING SHIT THAT WAS COOL!!” He gasped.

“LANGUAGE!” His mother warned.

“Sorry!”

////////////////////////////////////////

“Scan 50% complete. Please move the camera,” VEGA beeped.

Via the Praetor's built-in camera functions, VEGA manually mapped the landscape. Eventually, he graphed a 100-mile radius of the land.

“Scan 100% complete.” VEGA concluded.

The Doom Slayer viewed the map on his HUD. Nothing. No argent energy, no demons, especially no argent towers. Only Farmlands and nature.

He might as well have been on a barren planet.

Using the edge of his new blade, he lit a small fire and sat on the most comfortable rock he could find. He laid his helmet – VEGA with it – next to him. 

“I presume we’ll be staying here until nighttime.” The Slayer nodded. “The demons here cannot handle the sun, so they only appear at night. If there are any nearby, you can collect more samples and figure out more about them and this world.”

Silence. Wisty huddled next to the fire. The Doom Slayer petted the smol furball.

“I was not programmed to cook,” VEGA began, “but I can detect what is edible for the human body. I will scan the local environment.” VEGA scanned. “There is meat right there,” The A.I gestured at Wisty. Offended, Wisty angrily squeaked at VEGA and hopped away. Minutes later, a soft clang echoed from Wisty's direction. The Doom Slayer glared at VEGA.

“My apologies.”

He followed Wisty's trail. Hopefully, he hadn't gotten into any trouble.

////////////////////////////////////////

The Doom Slayer stopped at the foot of a large pine tree. Peculiarly, the tree had been burned to it's skeleton. Another metal THUMP rang at its roots. The Slayer found Wisty bouncing on a metal chest. He brushed the small creature aside (who angrily squeaked) and read the three big initials on the box.

U.A.C

The Slayer ripped the chest open and tore out a combat shotgun. He cocked the slider and caressed its shape. It was different from the one on Mars: Its barrel was longer, but it had practically the same capabilities, if not more, than the latter. The combat shotgun was fully loaded, with at least a hundred more shells crammed with in the chest. He pocketed everything and returned to the bonfire.

“You’ve returned Doom Slayer. Unfortunately, I was unable to find any ingredients for marshmallows.” The Slayer showed VEGA the shotgun. “Interesting. I thought the weapons here were vastly inferior to modern technology, yet this gun is of the same caliber as U.A.C weaponry.” Wisty grinned at VEGA and would have said ‘who’s dinner now buckaroo?’ had rabbits learned how to talk (a skill they thankfully never developed).

“You do have a habit of finding guns wherever you go. Perhaps you will find more familiar weaponry in this world.”

Silence.

“I agree,” Vega said. “It would make things much faster.”

Silence.

“If they are from the U.A.C, I do not understand why these weapons were sent here specifically. If they were to assist you, then they could have made it easier by sending it alongside the Praetor suit. The U.A.C isn’t known for its lack of precision.”

A question replacing another question. The Doom Slayer grabbed a few shells and rocks. The sun was still high in the sky.

He wanted to practice a little.

////////////////////////////////////////

Tanjiro enjoyed the rest of the day with his family. He tickled Routa until the little boy burst into tears and scampered away with his new toy. He cared for his mother’s fever despite her constant insistence that she was fine. He helped Takeo cut and gather the wood and told him how proud their father would have been. He talked with Nezuko about winter, how it was the coldest winter yet. Nezuko said she couldn’t wait for spring.

As the sun set over the Kamado's happy lives, he visited his father’s grave. He said his prayers and thanked his father for the Hanafuda earrings. He apologized for not buying more food for his family, but he promised he would make it up to them. To him.

After a brilliant dinner, they all huddled together for the night. Routa, scared, huddled next to Nezuko. Takeo, the third oldest, said he would bear the cold like a man, until he eventually asked his two younger siblings if they were lonely. Tanjiro simply slept in between all of them, the beautiful day fading like a dream.

That’s when he heard the knock on the door.

////////////////////////////////////////

_At the end of a corpse-filled telescope stood a small hut. He could hear people screaming inside. Fear. Anger. Hunger. His view quickly shifted throughout the scene._

_A green haori boy barely able to stand._

_A sick mother who could only cry for her children._

_Three siblings, all huddled together – the largest of them shielding them with his body._

_A girl with pink eyes lying dead on the floor. In her arms, a dead child desperately clutching an action figure._

_All very familiar._

_He suddenly grew short, very short, as if he were a toy. A man loomed over him._

_Prickled tendrils smoothed into hands. It picked him up._

The visions ended. The Doom Slayer grabbed Wisty before VEGA’s audio systems even uttered the words.

“I have detected Argent Energy.” He exploded down the mountainside. Down the same path he had traveled earlier today. Through the same trees he had passed earlier today. He grinded to a halt at the same house he had stayed in earlier that day.

The boy still stood. His legs had been torn apart by iron ribbons – pieces of his own bones piercing through his skin. His right arm was missing, and the entire left side of his face had been torn at. He still stood, a small axe in the slipping grip of his remaining arm. Tears streaked down his eyes.

“Are…are…they?” The boy shook. The Doom Slayer glanced at the blood and bodies inside the house. Eyes rolled. Cold skin, innards drooled out of bodies like soggy noodles.

They were dead. The little boy, the mother, the children– all of them. The Doom Slayer’s vision tunneled, focusing on that man from his visions. He cracked his knuckles.

“I…I couldn’t…I couldn’t do anything.” What little he had left died, and he slumped to the ground.

The Slayer stood over Tanjiro’s body. Wisty, traumatized, hopped away from the horrific scene.

“He is still alive, but his life signs are barely readable. Fortunately, I have detailed experience with human biology. I could give instructions on how to stabilize his condition.”

“But the source of the Argent energy is already a mile away, and its energy signature is rapidly fading. I won’t be able to track it soon. I’ll mark it on your HUD.” Just then, Wisty squeaked, beckoning the Slayer to look. Wisty was sniffing one of the corpses, his ears raised with hope. It was the pink kimono girl, Nezuko. “I am detecting a pulse from her. It is faint, but healthy.” VEGA added.

With a grunt, the Slayer rested the two siblings against the wall of their ruined home.

“Slayer,” VEGA added quietly. “I am detecting a foreign substance within her body. It is causing an abnormal change in the girl’s functions. It is identical to the substance I measured from the previous sample,” The Slayer froze. “That means…” VEGA decided to stop: deciding to be one of the few entities to live after seeing The Slayer pissed off. The Doom Slayer tied the nearest bundle of rope around the little girl. Just before he left, he gave Tanjiro his pistol.

With boiling blood he chased his prey.

////////////////////////////////////////

He ran like this for an hour, the Argent Energy signature growing dimmer and dimmer as he got closer and closer. Whatever it was, it was fast. Wisty nervously shivered against the violent wind. He squeaked every time they scraped a tree branch or boulder.

At the end of the hour he caught a glimpse of the source: a fine-suited gentleman with loose hair and an obsidian jacket, criminally styled; Identical to his visions.

“Sunrise is in another 10 minutes. Unless this demon can survive the sun, he will be cornered.” The ground cracked beneath him as The Doom Slayer ran faster.

////////////////////////////////////////

The demon suddenly stopped atop a frozen lake, his back turned to the Doom Slayer. The sun rose, but the snow-cloudy sky blocked its deadly rays from disintegrating the demon. He was waiting for something. Without turning around, he addressed him.

“You are persistent,” The demon mused. “I’d love to entertain you, but I am not in the best mood today. Go away.” 

A large house bursted through the icy surface. Like a leaping whale, it swallowed the demon and dived back beneath the waves, beneath the lake floor. The Doom Slayer watched as the massive infrastructure slowly burrowed into the ground.

“I detect massive movements underground. Supposedly, it is a massive mobile infrastructure at least several hundred miles long. There appears to be no way to access it now.” The Doom Slayer stared in silence.

“Signal lost.”

The Doom Slayer fired a round into the lake below. 

////////////////////////////////////////

She opened her eyes, her stomach rumbling.

_What’smynameIdon’trememberandwhyamItiedupbysomeannoyingrope._

She shook her aching head. It was hard thinking straight. It was hard thinking at all, as if her brain had been run through a blender.

_OhyeahandI’mhungrylikeIcouldeatahumanwhichisfinebecausehumansaretasty._

The only thing she could focus on was the human meat next to her. Its luscious nutrients made her mouth water. She wrestled within her bonds.

_heythisisannoyingIwanttoeatcansomeoneuntieme?_ She tried to speak, but was only capable of making basic grunts and shrieks. _Iforgotthattoo?fineI’lldoitmyself._ She gnawed away at the ropes. Finally freeing herself, she pounced at her prey.

A gunshot slugged her in the side.

_Owowowowowowowowowowowwhatwasthat?_

A man in a weird suit glared at her, a smoking shotgun aimed at her. She growled. _Heymindyourownbusiness._ He fired again. She barely dodged the bullet spread. _OKAYOKAYFINEDIE_

She bounced all over the place with her newfound strength.

_Okaythat’sagunIrememberthosesohe’llhavetoreloadatonepointandthenI’llgethim._

That didn’t happen. The man kept on shooting and shooting at her.

_Whatthehelldoeshenotneedtoreload?_ She decided to trade with a decisive blow. She charged into the shotgun. The shells gutted through her stomach, but she was within range now. She clawed at the stranger, but he was faster. He grabbed her arm and grappled her into a choke hold. Her hair brushed a silvery blade on the man’s arm.

_Idon’tremembermuchbutIthinkthosehurtalot_ She panicked. The blade extended, inching towards her neck. _Nonononononononononononono…._

A plasma shot bounced off of his helmet. The two turned to the shooter. Despite his injuries, the human meat was standing. His green Haori was wet with blood. A pair of Hanafuda earrings hung from his ears. _Seemsfamiliar…_

“Don’t…” His fingers trembled. “Don’t hurt her. She didn’t kill them. It was, it was…” He struggled to breathe. “a demon! A demon did this to my sister! To my family!”

The man’s grip tightened. _Couldyoudistracthimabitmore?_ She thought as she desperately gasped for air.

“I know what you are now! You’re…you’re a demon slayer! I recognize that scent! I know how things may look now but…” The boy vomited blood, his legs threatening to surrender. “But I can’t let you kill her. She’s...my sister.”

_I’mrelatedtohim?Iwonderwhoseolder.Doolderbrotherstastebetterthanyoungerones?_

“I promise she won’t kill anyone. Nezuko, she wouldn’t do that! And I won't let her! I’ll find the demon that did this, and…and I’ll cure Nezuko! Please!”

Her ears perked at the name. _Thatmustbemyname.Neat._

Silence. The stranger didn’t do anything more, and he didn’t do anything less, his grip still chained around her neck.

The human suddenly pleaded to her. “Nezuko! I know I couldn’t do anything. I’m sorry you had to suffer so much.”

She frowned. _What’shetalkingabout?Ithinkit’ssomethingimportant..._

“It hurt, didn’t it? But please, don’t give in! Don’t become a man-eating demon!”

“Remember! Takeo, Routa, Mom, Hanako, Shigeru! It hurts to remember them but please, please don’t forget them!”

She felt a sharp pain in her chest: A painful memory pounded at her heart, aching to be let out. Aching to be recalled. _Owwdon’tlikethatshutupplease_ She snarled at the boy. 

“Nezuko, please” his voice cracked; his tears stained the snow. The pain worsened.

_Pleasestoppleasestop_ she begged, but the words came out as only feral cries. Somehow, the boy understood her - his eyes flickered with hope.

“Don’t become a demon Nezuko! I promise, as your big brother that I’ll make all of this right!” Tanjiro fell to his knees, now begging to the man again. “Please....please don't....”

He didn’t flinch. It was curiosity, not pity, that stopped the demon slayer from killing her.

Slowly, he prostrated before the man. “Please. D...don’t kill her.” He whispered. She didn’t even remember this boy, but she couldn’t bear to see him so desperate. At the same time, all she could think about was eating him. Her mind tore itself apart, ravaging itself. She sweated profusely.

The man had heard enough. SCCHT, the Nichirin blade brushed her neck, drawing blood. But right now, the sharp pain in her chest felt worse than any wound from a Nichirin blade.

The rabbit next to her squeaked, terrified of what was about to happen.

She didn’t want to die, but she didn’t want to feel this pain, this anguish, that clogged her heart. _Justgo!Everyoneleavemealone!_ She pleaded.

With a sudden burst of strength, the boy aimed and fired a charged shot at the stranger. He hit the snow beneath the man. Then, two things happened: One, she felt the snow beneath the stranger’s feet liquify, becoming wet. Slippery. With her strength, she could unbalance the man. And she did. Both the stranger and his grip on her slipped. She was free.

Two, her momentum caused her to tumble into the snow, the cold snow that she had endured for the past several months. She hated it, but her family had a way of bearing with it.

_Ohrightbecausewe…they….wemakecharcoal…right?_ The world seemed to crawl to a halt. Her mind cleared a little, just a little. _Thatshould… That should be my house. The Kamado’s house. It was home to a widow and five children. One of them was called…Tanjiro._ Her heart jumped at the valuable memory.

Her eyes darted to the boy. She remembered how he had a patch-like scar on the left side of his forehead. She remembered his brotherly smile. The pain worsened, but the trickle of memories made it seem numb. They were her guiding light, like a torch in a dark tunnel of the future.

Behind her, the stranger reached out to grab her. Ahead of her, Tanjiro had passed out. To her right, a wild expanse of woods to lose herself in. She could just run from it all, free herself of all the despair.

She was on thin ice – not knowing what to do, only knowing that she had to decide.

The ice cracked.

She leaped to Tanjiro and caught him before he hit the ground. She cried as she hugged her brother's bleeding body. _I don’t remember much, but I won’t let anyone take anything I care about. Not… Not again._

_////////////////////////////////////////_

The Doom Slayer glared at Nezuko. “It seems as if she is stable.” VEGA noted. “She hasn’t eaten the boy yet.”

The Doom Slayer’s fingers brushed the trigger. If he shot now, he would hit Tanjiro, not that it matter now. His injuries had gone untreated, it was obvious he would not survive. Tanjiro vomited another torrent of blood. Shrieking, his sister laid him on the ground, piling snow on top of his body.

“The boy has an abnormally high fever. She is trying to cool him down.” VEGA observed.

The Doom Slayer noted the tears streaking down the demon’s eyes as she desperately tried to heal him. She even ripped parts of her kimono to close the wounds. He glanced at Wisty. The rabbit sadly squeaked as he lowered his head in mourning. 

“Slayer?” VEGA queried. The Slayer lowered his weapon.

The Doom Slayer approached Tanjiro. Nezuko barked at him to stay away. He kicked her aside and knelt next to Tanjiro.

“Manual controlled authorized. The Praetor suit, however, has no functions that could help…” The Slayer put Tanjiro’s hand into the Praetor suit’s left glove. Red lightning cackled from his right glove, he pressed the two together and forced the Argent energy into Tanjiro, like a defibrillator. He did it again. And again. And again. Nezuko clawed at him to stop, but the Doom Slayer ignored her. On the fourth press, Tanjiro's body shuddered with life. His wounds miraculously closed; his lung relaxed; His breaths calmed. Slowly, Tanjiro opened his eyes: A mixture of shock and relief washed over him. Nezuko cried as she checked Tanjiro.

“S-sorry for making you worry.” He weakly smiled. The former-human cried and hugged her brother, shaking him relentlessly. “Ow ow ow ow ow.” He bleated.

Suddenly, The Doom Slayer collapsed next to Tanjiro, as if he were the one in need of help. 

“Doom Slayer, are you all right?” VEGA asked, his concern masked by his apathetic audio systems. The Slayer nodded as he slowly picked himself up. Soon he brushed off the fatigue as if nothing had happened. “Using the suits systems that way was interesting. Should I short-cut it as a feature?”

Silence.

“Understood: Request denied.”

“Tanjiro’s condition is now stable. However, he requires proper medical skill and equipment in order to fully recover. Unfortunately, I lack both appendages and sanitary utensils.” The Doom Slayer looked at the two siblings – hugging and crying as if it was their first time hugging and crying. 

A warm feeling rose in his chest. He beat it to make sure it wasn’t some weird malfunction in the suit.

////////////////////////////////////////

Inside his Dimensional Infinity Fortress, Muzan could finally think. He, the immortal who possessed five brains, needed time to think. In one hand, he held a human skull with red hieroglyphics etched over its skeletal frame.

He had found it in his Husband Disguise, on the tree he had planted outside of his ‘family home’. He liked trees. They were predictable and simple: They knew their place and did nothing but follow their fate. He wished some of his demons – a few Moon demons especially – could follow their example. He had always wanted to plant such demons into the dirt and see if they could grow from the experience. The sun always disagreed, the bastard thing.

One day, a cloudless lightning bolt struck the tree, mutating it into a rotting, dead tree overnight, with the odd skull hanging from it’s branches like a fresh apple.

His neighbours' called him an accursed demon the day it had happened, and they vehemently attacked him when he took the skull. Even when he had settled that insignificant matter, the skull itself attracted a lot of undesired attention. Still, he refused to let it out of his sight. He recognized the power it held for him.

In his other hand was a small action figure: A green toy soldier in a punching pose. He clicked a button on its back, and the figure played a little guitar riff. He slowly brought the two items closer again. The red hieroglyphs grew darker shade of red, as if it was scared. When they touched, the skull’s jaw stretched open and shrieked.

Visions of blood skies and alien mountains blurred his vision. They swirled into a telescope over a fierce battlefield. On the corpses and corpses of dead monsters, a single man towered over the hellish pile, identical to the figure in his hand. The man, the slayer, saw the observer, the demon. He cocked his shotgun.

With a lead BANG the visions abruptly ended.

_Strange_ Muzan thought. _What exactly is this thing? And who is that man?_

////////////////////////////////////////

On a mountainside hundreds of miles away from Muzan, two children finished burying their loving family. They said their prayers, they left their tears, and slowly packed up their belongings. The unchained predator impatiently waited for them.

Nezuko covered as much of her skin as possible to guard herself from the sun. Tanjiro was still too weak to walk, so the Doom Slayer had to carry him. Wisty generously gave up his shoulder spot to Tanjiro and slept on the opposite shoulder. 

The Doom Slayer checked on Nezuko. She couldn’t talk, and instead she gave him a thumbs up. She was ready.

The sight of her dogged canines blazed a hellish rage inside of him, but he held himself back. They were ready to leave.

Suddenly, the Slayer looked at the vast land behind him, as if someone was spying on him. 

“Is something wrong Kame?” Tanjiro asked. 

The Doom Slayer fired his shotgun at the invisible watcher.

He didn’t know what it was. Soon enough, it would know what he was.

Rip

And

Tear

Until it is done.

////////////////////////////////////////

**Notes for the Chapter:**

> Author’s note:  
> The reason why the writing from Nezuko’s point of view is weird is because it’s from the perspective of a wild demon’s mind. It is unorganized and it’s hard for her to think at first, but she gets used to it. It’s something I wanted to use to emphasize why demons typically lose control of themselves so often. Please comment on any grammar mistakes or questions, and I will strive to edit such errors. Also comment your questions so I can strive to make the work easier to understand. Hope you enjoyed.


	3. COVID - 19 of The Slayer

An endless demon horde charged at the Doom Slayer. He cocked his super shotgun, ready to meet them en masse. Suddenly, a Revenant crumbled onto the ground, finding itself short of breath. Around him, the other demons started coughing. A Mancubus vomited its last meal – a human corpse. Cacodemons grumbled with a fever. A Pain elemental coughed up lost souls. The whole demon army fell into a fit of fevers and fatigue.

Tanjiro and Nezuko kept their distance from the demons. “VEGA what’s wrong with them?”

VEGA chuckled. “What you are seeing here is the result of one foolish Demon: A single Revenant who failed to take the proper precautions against the Coronavirus, also known as tbe COVID - 19. He thought the whole epidemic was nothing but hogwash: an exaggerated flu. Besides, even if he got it, there’s an average 3-4% chance of dying due to COVID - 19, and he’s not even alive!”

“Is your voice okay VEGA? It sounds a bit more…cheery than usual.”

“It’s tip top on the block, son!”

“Son?” Tanjiro said, utterly confused. Nezuko frowned.

“Let’s use this ill-educated Revenant as an example.” A drone displayed a holographic replay from two-weeks ago.

People ran as the demons swarmed the hospital’s facilities. One demon – a Revenant – crashed into the room of a sick man. The man screamed as the Revenant devoured his innards. The video paused.

“Keypoint 1: Keep a distance of at least a meter away from victims. COVID - 19 is very easy to spread. It can stick to any object that a victim touches, and infects a person as soon as it enters a host through their eyes, nose, or mouth. In this case, it has entered the Revenant through the mouth.”

“If you’re in a situation where you must interact with people daily, take some basic precautions to protect yourself. For instance, avoid touching your face in public. Make sure to thoroughly wash your hands with soap for at least 20 seconds. You could also wear gear to protect yourself.” The Doom Slayer flashed his Praetor suit – a Makyr-quality epidemic-protection suit, “but a simple mask is enough. Remember that the COVID – 19 can and will stick to objects, so make sure to wash your belongings too when necessary.”

The video continued. The Revenant rejoined the demon army, flying over the battlefield with his jetpack. It screamed as it rained down hell upon its enemies alongside its blood-born comrades. The video paused.

“Keypoint 2: If you end up getting the Coronavirus, it’s your responsibility to not spread it. Don’t travel unless absolutely necessary. Try and arrange a meeting with your doctor over the phone for possible treatments to reduce it's affects. COVID - 19 is very easy to spread. Furthermore, even if you survive it, you shouldn’t try to spread it to others. The most vulnerable demographic is young children and the elderly.”

The Revenant, sadly, flew next to an elderly Pain elemental and its young Lost souls. The Revenant patted the Pain elemental and flew away.

“Otherwise, the virus will spread more and more as more, and more people (or demons) will suffer. Symptoms include fever, dry coughs, and a feeling of being short of breath. Unfortunately, COVID - 19 is a slow burn and it can take at least 2 weeks before its symptoms become fully apparent.”

Tanjiro looked at the sick forces of hell. He shivered. “What else can we do?”

“Prevention is the best way to stop epidemics like these. Your primary option should be to reduce close contact with others. In other words, social distancing. Washing your hands every time you go into public and not touching your face are also ways to ensure you don’t carry the virus. You should also exercise a little to make up for the stationary situation of quarantine. However, in very specific situations where the hosts are inhuman demons from Hell,” The Doom Slayer cocked his super shotgun, “social distancing is the optimal choice.” The Doom Slayer ripped and tore through the horde of demons.

“And if you’re feeling down because of this epidemic, remember kids,” VEGA reminded.

“COVID – 19 may take months to solve, but DOOM is ETERNAL.”

(Link to learn more about COVID - 19):

[World Health Organization - Coronavirus](https://www.who.int/health-topics/coronavirus#tab=tab_1)

**Notes for the Chapter:**

> F in the comments for every Demon that got COVID - 19.
> 
> In all seriousness, please stay safe during this COVID - 19 epidemic. Cherish your loved ones, spend your newfound  
> free time resourcefully, and rip and tear!


	4. Doctor Of The Slayer Part 1

**Notes for the Chapter:**

> Author’s note: This is the longest chapter I have ever done, and it’s not even the whole thing yet. This is split into two main parts. Please comment on any errors I made.  
> Spoilers:  
> Introduction of a character from episode 15 of Kimetsu No Yaiba anime.  
> Also, I’m still 100% set on Shinobu getting a chainsaw.  
> Also, I have a friend called Monoxidev2 who beta-reads my story. So thank you for helping Mono!  
> And enjoy the story.

////////////////////////////////////////////////////////////////////////////////////////////////////////////

_ \- TWO WEEKS AGO _

_ U.A.C – Mars - Lazarus Lab, Site A – Main Computer _

_ /////////////////////////////////////////////////////////////////////////////////////// _

_ [IDENTITY CONFIRMED: Welcome, Samuel Hayden] _

_ /////////////////////////////////////////////////////////////////////////////////////// _

_ [RUN LAB DIAGNOSTICS] _

_ [ACCESS SECURITY SYSTEMS] _

_ [DOWNLOAD] _

__ _ [Download files] _

__ _ [Downloading coordinates] _

__ _ [Download complete] _

_ [OTHER] _

_ [ACTIVATE TETHER] _

_ [CHOOSE LOCATION] _

__ _ [Input coordinates:] _

__ _ [Earth] _

__ _ [Hell] _

__ _ [Project Phineas Passage V 2.0] _

__ _ [location: secured] _

_ [Paraphernalia: confirmed] _

_ [Energy levels: sufficient] _

_ [Warning! Precision will be decreased by a projected 79%] _

_ [Are you sure you wish to proceed? This action cannot be undone] _

**_[_ ** **_YES]_ ** **** __ _ [NO] _

__

_ [Confirmed. Tether activating in,] _

_ [T-5] _

_ [T-4] _

_ [T-3] _

_ [T-2] _

_ [T-1] _

_ [Tether activated.] _

_ /////////////////////////////////////////////////////////////////////////////////////// _

- _ PRESENT  _

Nofu wallowed in the fresh new day. The sun was shining, the weather was ripe, his wagon was being stolen, a cool breeze seeped his bones.

“HEY!” Nofu yelled at the culprit. It was the same stranger from a few days ago, his verdant armor gleamed in the sun. “YOU AGAIN? BASTARD! THIS TIME I’M GOING TO SEND YOU STRAIGHT TO HELL!”

The stranger fled for his life – the wagon trailing behind him. Nofu chased after him. (Though as we readers know, it should have been the other way around).

//////////////////////////////////////

“He…can definitely run.” Nofu panted. Hidden, he saw the stranger stop next to a wide cliff face. A scarred boy in a green haori waited for him.

“Did you pay for this?” The boy asked.

Silence.

“Hey! You can’t just take something without paying for it! We have to go back there.”

Silence.

_ Is the boy talking to himself?  _ Nofu wondered.

“First things first.” He crawled into the hole.

Nofu gasped. Weak children. Wagon. Single adult. It all made sense. He puffed up his chest like a chicken.

“Ho!” The verdant man glared at him. “Bastard! Don’t think I don’t know what’s going on!” Nofu glared back. “Thought you could abandon them here huh? Leave them be?”

Silence.

“What? Cat got your tongue? Scared that I’ve caught you red handed?” The old man tsked. “You should always take responsibility of your children. It’ll hurt more if you don’t.”

“Kame? Who’s there?” The boy called.

“Oh? You’re not just a criminal, you’re Kame the criminal!” Nofu yelled. The boy peaked his head out.

“Are you the one that Kame took the wagon from?” He asked.

“Why yes I am. I would very much like to have it back.”

He sighed. “Sorry. We really need this wagon. It’s hard for me to walk, and my sister is sick.” Nofu’s steel heart melted at the boy’s honesty. “I’m Tanjiro. This,” He pointed at a small girl huddled inside the cave, “is my sister Nezuko.”

“Looks more like a mole to me,” He joked.  _ Seriously, did she dig a hole for herself? _

“The man helping us is Kame.” Kame glared at him. He had a new blade attached to his arm and another thick bicep ripped open.  _ Show off.  _

_ He only took the wagon and some bamboo. I can manage without them. And if it’s for these children… _

“So, you really need this?” Nofu reluctantly relaxed. “Alright. I gotcha. Thanks for the explanation.” He glared at Kame. “Unlike SOME people, I know how to be civilized.”

“Do you two…know each other?” Tanjiro asked.

Awkward silence. Kame loaded the siblings into the wagon. With his remaining arm, Tanjiro swaddled Nezuko in a mountain of clothes. So many that no light touched her skin.

_ Talk about being smothered in love.  _ Nofu chuckled. “Where you heading?”

“There’s this big estate we saw on a map; North of here.” Tanjiro pointed to their general destination. “Kame and I think it’s a place of healing.”

Nofu frowned “The rumored ‘Butterfly Estate?’ I’m surprised you found it on any map.”

“The Butterfly Estate?”

“Supposedly it’s this mysterious estate run by a great doctor. If you can find it, there’s no doubt that your medical problems would be solved, but nobody really knows whether he or the estate are actually real. No roads or normal maps lead there, and the scant few that claim to have seen it usually forget it’s location, like they were drugged. Or possessed by ghosts, if you’re into nonsense.”

“Oh,”

“Plus, it’s as far as it is mysterious. You have quite the distance to walk.”

“Oh.” Tanjiro lowered his head. “But we have to try!” He winced as he stood up. “We can’t just stay here and do nothing.”

_ He’s got spirit.  _ “Right on!” Nofu cheered. “Safe travels Tanjiro!”

“Thanks!” Tanjiro gave him some money. “Here. I know its small change, but it should be enough.”

“What?” Nofu refused. “I can’t let some poor kid give me money. The shame would kill me! You can have it all for free.”

“No. I know how much these things can cost, let me…”

“Nope!”

“But I have to repay you!” Tanjiro declared.

“Nope!”

“Yes!”

“Nope!” He pushed Tanjiro and his money into the wagon. Promptly, Kame picked up the wagon and sped away.

With a surprising amount of strength, Tanjiro flung the coins at Nofu’s head.

“THANK YOU!” Tanjiro yelled as the wagon sped away. “PLEASE ACCEPT THE MONEY EVEN IF IT’S NOT ENOUGH FOR EVERYTHING!”

“YOUR WELCOME!” Nofu yelled. “AND I’M NOT PICKING THEM UP!”

//////////////////////////////////////

“It’s night time, Nezuko. You can come out now.” Slowly, Nezuko burrowed out of her blanket cave. She cautiously stepped into the moonlight. Tanjiro looked at her again. Something was off…

“You look smaller…” He noticed. “Can you shapeshift? Can demons do that?” He asked The Doom Slay-Kame.  _ Doom Slayer? I’ve never heard that name before. _

Kame didn’t respond.

“I know you don’t talk a lot, but it would be really nice if you could give us some more information.”

Silence.

Tanjiro sighed. Recently, it had felt like he was all alone. It had only been a few days since the incident, but it had felt like years.

Everyone he loved, suddenly dead. Everyone except his little sister, Nezuko.

A small part of him believed that even Nezuko was gone: she had forgotten everything about her human life. Her voice worked, but she had forgotten how to talk. Her hair hung loose, but she didn’t seem to care. Nezuko loved - or had loved - her hair. She didn’t even show any remorse over her kimono. Several times he had to remind her to raise it so that she didn’t drag it along the ground.

Worst of all, it seemed like she barely remembered anything about the Kamado family. When he got her to respond to simple YES/NO answers, she answered YES to general questions about the Kamado family and NO to any specific details, like birthdays and habits. The fact was hammered into him when he tried to start a conversation with her:

“How’s your day Nezuko?”

She nodded.

“Do you remember my name?”

She nodded.

“How’s the weather?”

She shrugged.

“Do you want to fix your Kimono? I think I still have some needles from our home.”

She frowned.

“Well, you never wanted to replace it. Every time it broke you would stitch it right back up. Remember?”

She shook her head.

“What about your walks with Routa? Remember?”

She shook her head.

“Wait, remember the time Takeo tried to prank you by putting ice in your kimono? You complained about it for weeks!”

She shook her head.

“So, I’m hungry. Let’s eat; what’s your favorite food again?”

She responded with awkward silence (Tanjiro could guess what the answer was).

He sighed again – a bad habit he had recently developed. _ I can’t lose hope. It’s already a miracle that Nezuko and I survived. I just have to keep on going and figure things out as I go. _

Which brought him to another pressing matter: Kame.

It was Kame who guarded them throughout the journey. Whenever any of them got tired, he just carried them on his back. The only breaks he took were when Tanjiro or Nezuko needed them. During those breaks he wandered – Wisty at his side – and returned with the ashen remains of some unfortunate demon he found hiding somewhere (A burning reminder of what Nezuko could become). He didn’t eat, sleep, or rest.

The last one was partially true. On a few occasions he had found Kame relaxing: Either petting Wisty, listening to a black device, or maintaining his gun. (Tanjiro swore he once found him playing something called a “Nintendo Switch.” When he asked Kame about it, Kame forced him to walk bare-foot for the entire day.  _ Where does he even have the space to put that thing?  _ He had wondered).

Was Kame human? Tanjiro knew the answer, but he constantly doubted it.  _ No way. No human could walk through Hell and...  _ He stopped.  _ I need some sleep.  _ He thought. Sleep deprivation was another bad habit he had picked up.

He talked to Wisty to pass the time.

“How’s your day?” Wisty squeaked.

“Oh? What makes it so special?” Wisty squeaked.

“Really?” Tanjro gasped. “And what was this bunny like?” A loud scream pierced the air.

“Hey hey hey! No need for that kind of language!”

Distracted, He was slow to realize that the wagon had stopped at the foot of a hill. At the top, a warmly-lit house stood. Kame was gone.

“Hey, where’s Kame? “ Nezuko pointed at the house.

Seconds later, a demon was thrown outside of the house. The demon’s scent was a drop of water in an ocean of blood when compared to the one that had attacked his home. Still, Tanjiro's nose screamed at the horrible stink. The demon desperately crawled to them.

“Please kid you’ve got to hide me.” The demon pleaded to Nezuko. He kicked the demon aside.

“Nezuko stay back!” He said. Nezuko angrily snarled at the demon. The demon frowned. A demon and human, working together? Kame answered the demon with a foot-stomp and head-slice. The confused demon dissolved into still-confused ashes. The palpable air in his lung relaxed. “W-wow. So quick…” He shuddered.

Wisty squeaked happily. He bounded back onto Kame’s shoulder.

“Oh my!” A soft voice called from the house – from a petite woman. She beamed at the motley group. “You killed him for me. Thank you.” She sized-up Kame. “You’re quite strong, aren’t you?” she said, her face twinkling in the night.

Silence. Kame picked up the wagon. Tanjiro kept staring.

The woman was something straight out of a dream: Her shoulder-length hair faded from black to purple as his eyes traveled down her hair; tied back in a yakaimaka style by a butterfly pin. She wore a white haori that mimicked a butterfly’s wing, colored in a gentle gradient from white to a cherry-blossom pink, left to freely flow in the wind. Indeed, she was a butterfly made human: Small, light, fragile. Ethereal. He blushed.

“Please, come inside. I have to thank you for killing that demon for me.” The woman smiled.

Silence. Kame glanced at the woman. At her unique buttoned uniform, to be precise.

“He doesn’t talk much. Sorry.” Tanjiro said.

“Oh? You talk for him?” She asked.

“Sort of,” His stomach grumbled; they had some money left. “We’ll eat only what we can afford.”

“Don’t be so generous, Mr…”

“My name is Kamado Tanjiro. This is my sister, Kamado Nezuko. That man is Kame.”

“Kamado Kame?” she teased.

“No. He doesn’t have a last name.”

“Ah, I see. Come here Kanao! We’re going to have dinner together!” A young girl suddenly appeared behind him. Tanjiro jumped out of the wagon. _Where did she come from?_ __

“That is my apprentice, Tsuyuri Kanao.” The butterfly women bowed. “My name is Kocho Shinobu. It is a pleasure to finally be acquainted.”

//////////////////////////////////////

Tanjiro sat next to Nezuko. Shinobu and Kanao sat at the opposite side of the siblings. The Chabudai table made Kame stand out like a bear at a rabbit’s tea party. He sat at the end of the table.

“Kanao? Could you please cook for me today?” Kanao aloofly went to the courtyard and started a small cooking fire.

“No kitchen here?” He asked.

“Nope. The owner left with all his belongings.”

“You’re not the owner?”

“Yes. I’ve actually come here to steal his hidden treasures…” she giggled. “Just kidding!”

“Then why did he leave?” Bored, Nezuko sharpened her fingernails. Kame shared her enthusiasm and discretely wiped his blade – Wisty relaxing on his shoulder.

“He recently suffered from a terrible ailment. I gave him some medicine to stabilize his condition, but I recommended that he be treated by a more experienced doctor. For now, I’m watching over his home.”

“You’re a doctor?” He was intrigued.

“Medicines and maladies are my profession,” Shinobu chirped.

“Oh! Then you must have heard of it: the ‘Butterfly Estate!’”

Her eyes glittered. “That silly rumor? I certainly hope you aren’t looking for it. A perfect doctor like that would run me out of the job.”

“That would be horrible.” He emphasized.

“Of course.”

“We still need to find him.”

“Of course.”

“Sorry.”

“That’s just how the health industry works.” She shrugged.

“We don’t have any good doctors near where I live. Hopefully, this doctor is good enough to treat all of us.”

“You mean you and your sister,” she pointed out. “your friend seems perfectly fine.” She glared at Kame’s blade. “Nice sword.” Kame met her glare.

_ SHINK _ , the silvery blade extended with the words _KILL_ written in Kanji. 

“Amazing!” Shinobu clapped. “Anyway, why don’t I do a check-up on all of you? Free of charge!”

In just a blink her face was uncomfortably close to Tanjiro’s. The room felt several degrees hotter. He smelled a slight aroma off of her. It was…Wisteria?  _ Is it her perfume?  _ He opened his mouth – to ask about the smell or the sudden temperature change, he didn’t get the chance.

Shinobu waved her finger. “Nu – uh. Don’t talk. It’ll make the examination harder.” She pulled out a stethoscope and examined Tanjiro’s body.

Examined. With her hands.

Nezuko had a mischievous grin on her face as she watched Tanjiro blush.

“Amazing. Almost every bone in your body was broken. I can tell from all these little cracks,” She rubbed his chest. “and you’ve suffered hundreds of deep cuts. Based on how fresh they are, you suffered all of this simultaneously.” She gave him a kind smile. “You should be dead. Congratulations!”

“Yay?” he half-heartedly cheered.

“Better yet, I think…” she squeezed the side of his chest. “Yup! One of your lungs is broken.”

“I…need that to live though…”

“It’s fine. You’ve got two lungs, just like you’ve got two eyes!” she poked the eviscerated left side of his face. “Hmm…it’s heavily damaged.”

Tanjiro nodded.

“Now don’t flinch,” She gently opened his left eye. “It’s been pierced, but your eye seems fine. If given proper treatment you should be able to see out of it again. A little.” She smiled at him – the same smile that butchers use for sick little pigs. “Really, I don’t see why you’d need to see a miracle doctor when you’re able to recover from something like this!”

Tanjiro shuddered. The memories flooded back, but he immediately damned them back. He wasn’t... he wasn’t ready yet. His body noticeably twitched. “Y-yeah,” he muttered.

She didn’t seem to notice. “I’m just going to check on your heart now.” She placed the stethoscope against his chest. “Hmm. Steady, but a bit too jumpy. Are you calm?”

“Yes,” he said.

She leaned in closer. “Sorry. Can you say that again?”

“Yes,” his face reddened.

“And tell me,” she whispered, her cheek so close to his. “did your friend Kame do this to you?”

Stunned, he immediately answered. “N-No.”

“O-kay!” she clapped. “I’ll check on your sister now.”

Nezuko hissed at Shinobu. “Calm down, calm down. I don’t smell that bad.” She held her still as she examined her body.

“No surface wounds,” she muttered. “And a bit of a shallow belly. Have you been eating?” Nezuko reluctantly shook her head. “Oh? Can’t talk?” she shook her head again. “Oh, you poor thing.” She hugged her. Nezuko squirmed in her grasp. Clearly, she saw this woman differently. “Now could you open your mouth for me?”

Hesitantly, she opened her mouth. “Wow. What big teeth you have!” Shinobu smiled. “Especially those fangs. They could pierce a man! Otherwise, you’re a healthy human.” She patted her head.

Tanjiro was confused. Shinobu acted so nice and kind, but she had this weird smell about her. It was jaded and sharp, fragranced with that odd smell of wisteria.

It was oddly similar to Kame’s aroma, only slightly less angry. He knew how weird he sounded: the idea that he could smell someone’s feelings. But a lot of weird things had happened as of late.

“You need me to check your bunny?” She asked.

Kame pulled Wisty closer to him.

“I think they’re good.” Tanjiro said.

Kanao came back with several bowls of fresh soup. She laid a bowl for each of them. Each of them, except for Shinobu and herself. “Not hungry?” He questioned.

“Small appetite, small body,” she smiled.

Kame ignored the bowl completely. Wisty happily licked the soup. Nezuko poked it, but didn’t seem interested.  _ So it’s only me and Wisty who want to eat.  _ His stomach growled in agreement.

It smelled intoxicatingly good. His mouth watered. But, against his desires, He ignored the bowl. He smelled something delicate mixed in the soup. A hazy, sleepy smell that tugged at Tanjiro’s suspicions.

_ A drug. _

Tense silence swelled within the house; the walls creaked from the pressure.

“So, none of you are hungry?” They all shook their heads (except Wisty, who was suddenly feeling very sleepy).

“Then we can skip to dessert.” A reflection flickered within her belt – the ornate grip of a sword. She looked at Nezuko. “How many people have you killed, demon? It’s an embarrassing secret, I know, but it’s good to get it out of your chest. You can use your hands if you need to.”

Nezuko vehemently shook her head.

“Nezuko hasn’t killed anyone.” Tanjiro defended her.

“Demons don’t tend to do well with humans,” She magnanimously explained. “And, really, there’s no consistent way to be sure she hasn’t eaten a  _ few _ .”

“You can smell the scent of blood off of them.”

She shrugged. “True. Unfortunately, I’m not a dog.”

In the blink of an eye, she unsheathed her sword (a customized rapier, to be exact) and stabbed at Nezuko. The poisoned tip stopped inches from her face – the blade stuck in the flesh of Tanjiro’s hand. He grimaced as blood seeped from the pierce. Nezuko snarled.

“You keep making things so hard.” She exasperated. “Kanao, could you please handle her?”

Kanao withdrew her own blade, a traditional katana partly colored pink. Tanjiro noticed the Kanji ‘KILL DEMONS’ written on the blade.  _ Demon Slayers? So Kame isn’t actually with them… _

Kame, meanwhile, grabbed Kanao by the leg and threw her through the wall. Neither Kame nor Kanao verbally expressed any surprise, pain, or effort to these events.

Fights were very anticlimactic when both fighters are quiet.

Kame threatened Shinobu with the loaded-end of his shotgun.

She smiled. “Oh. I forgot about you.”

Purple smoke billowed out of her clothes. The gas quickly spread throughout the entire room. The blade slid out of his hand. He rubbed the wound and choked on the gas. It was suffocatingly thick and hard to breathe. Nezuko reacted much more violently to the gas. She shrieked as the gas seemingly burned her skin.  _ It’s like she’s allergic to it,  _ He worried.

He picked her up and ran out of the house with Kame.

The moonlight cast a Shinobu-shaped shadow on them. She was on the roof - her petite body towered over them.

“So, you really aren’t a demon. My wisteria gas can enter through the skin, so it isn’t because of that weird helmet of yours. Good to know.” She said to Kame. “It’s amazing that you beat Giyu so effortlessly. Of course, he’s always so negative about his own feats. I bet he exaggerated some of the details.” She ranted to no one in particular. “And he treats Urokodaki with too much praise. I don’t doubt Urokodaki’s accomplishments, but he’s way past his prime. Let him rest! I volunteered in his stead.”

With a soft click, she drew her blade again; a strange new poison dripped from its tip. “With this, our difference in strength won’t matter.” She gleamed at Kame.

Kame glanced at Tanjiro’s pierced hand. “Don’t worry about him. He isn’t a demon, so he’ll be fine.”  _ The blade was coated in some kind of Wisteria poison. If that affects demons, then Nezuko… _ he glanced at his little sister.

Nezuko clawed at her neck – drawing long blood marks around her throat. Her eyes were bloodshot. She screamed as the poison ran its course, her body uncontrollably shaking.

Meanwhile, Wisty drunkenly sneezed purple smoke.

“Nezuko! You’re hurting yourself!”

“Hmm…. I knew the gas was nowhere near as strong as I’d like.” Shinobu muttered.

“Hold on. Demons are weak to wisteria?!” Tanjiro yelled.

“Yes.” Shinobu said.

“Then you can see Kame isn’t a demon! He’s human to the core. I know he might smell like a demon…” Tanjiro began

“He did smell a bit funny,”  _ cha-CHINK!  _ Kame cocked his shotgun.

“But he’s the one who saved me and Nezuko from demons! You shouldn’t fight him!” He argued.

“Well, look at it this way,” Shinobu explained,” the Demon Slayer Corps are the only defense for humankind against the demons. Anything that poses a threat to it is as much of an enemy as any demon.” She smiled at Kame. “I’m sure you understand, right?”

Silence.

“Yeesh, just like Giyu.” Shinobu sighed. Kanao leapt to her master’s side. “This poison won’t kill you Kame, but it will paralyze you for a very long time.” she smiled. “You can tell me how my poison tastes with the other Hashira!”

Tanjiro bit his lip.  _ This is bad. It’s all one big misunderstanding: Nezuko would never kill someone! And Kame only kills demons! What did he even do to them? But if Kame doesn’t fight back, he’ll be in trouble. That means he’ll probably kill them first...  _ “Kame! Please don’t kill them. They’re still humans!”

Silence.

Shinobu dived at Kame. Kanao leapt at the two of them. Tanjiro focused on Kanao.

He hadn’t fully recovered yet, but he could still fight. He pulled himself together.

Kanao charged right at him. He was ready this time. He pulled out a pistol and fired off a flurry of shots. She dodged every shot. Q _ uick!  _ He awed. With a weightless jump, Kanao leapt over him.  _ Crap! She’s going for Nezuko! _

“Run Nezuko!” he yelled.

Kanao swept at Nezuko - flowers flowing out of her blade. _I hope I_ _ ’m not hallucinating that,  _ he muttered as he kept firing at her. If she had any trouble fighting Nezuko and Tanjiro, her aloof face didn’t show it.

Nezuko did well, at first. But the drug was taking its toll. Her movements grew heavy. Kanao’s cuts were getting deeper and deeper. She suddenly seized up and stumbled to the ground – eyes shuttered in defeat. Kanao’s blade hovered over Nezuko’s head – her eyes devoid of remorse.

She deflected Tanjiro’s shot from behind.

“Wow…” he breathed. “She’s good.”

//////////////////////////////////////

Kanao stared sadly at him. She glanced at the demon. She was asleep. Without a word, she flipped her coin. Tails.

“Why do you keep on fighting?” she asked.

“Because she’s my sister. She hasn’t killed anyone, and she doesn’t deserve to die.”

She flipped her coin again. Tails.

“We humans aren’t very good at resisting our temptations and instincts. Despair, greed, lust, hunger. Demons were human. Are you sure she won’t do it at some point?” she asked.

“She’s my sister, of course she’d never do that! Besides, I won’t let that happen,” he declared. “I won’t let her die a demon. I know I can find a cure to fix her!”

She flipped her coin again. Tails.  _ Weird luck,  _ she thought.  _ Three tails in a row. _

“Are you planning on getting your friend to help? He doesn’t seem to care for you sister very much. I saw. When Shinobu attacked her, he didn’t do anything to stop it. He hates demons.” _ Probably more than Shinobu.  _ Kanao thought.

“I know! I know I can’t rely on him to help her.” Tanjiro yelled.

She flipped again. Heads. She silently looked at him. His dismembered arm, the ruined left side of his face.

“I can’t stop now,” he said, as if he read her mind. “because if I don’t keep trying, if I don’t push myself to hell and back, what will I have to show for it? I could die right now: Nezuko would stay a demon, and nothing would change. But I have to keep trying if I want to see a future where things are better. Where I can avenge my family, and where Nezuko can walk in the sun again.”

Kanao flipped her coin. Tails.

“You aren’t the only one to suffer at the teeth of demons,” Kanao said.

“Then I’ll do it for them too. For all the people who suffered at the hands of demons, for a future where things like that don’t happen anymore: To stop Muzan Kibutsuji!”

Her aloof face faltered slightly.  _ He truly met him. His sister was evidence of it, but this confirms it. _

“That’s why…I’m sorry.” He grabbed her by the shoulder.  _ What’s he doing? _

Tanjiro head-butted her into the ground. It wasn’t enough to knock her out, but it left a bleeding dent on her head. “Uh…are you okay?” he asked ironically.

She shoved him aside and sought to finish her work. She thrusted her blade at Nezuko. A soft, drunken squeak echoed.

//////////////////////////////////////

Nezuko wanted to puke. Butterflies danced in her stomach. Very sharp, painful butterflies with poison-tipped needles. Whatever was in that gas, she never wanted to breath it again. Her body felt stiff, but her senses were slowly coming back to life. Something white was on her face.

She touched it. Furry. Soft. She picked it up.

A dizzy Wisty wiggled in her grasp.  _ Aww. Cute. _

Inches above him, the silvery tip of Kanao’s blade hovered patiently.  _ SHITWHATTHEFUCK. _

She rolled out of the way. Kanao’s blade missed.  _ She was going to attack, but stopped because Wisty was in the way. _

_ Did Wisty just save my life?  _ She looked at the intoxicated bunny.  _ Thank you _ . She petted him. If Wisty had opposable thumbs, he would've given her a drunken thumbs-up. She dropped him off somewhere safe.

_ Alright,  _ she growled at Kanao,  _ Let’s try this again.  _ She readied herself like a panther.

She’d been holding back her instincts for a while, but now was the time to let loose!

_ Allrightlet’sdothisherewegoTanjirowon’tmindifIeatthemright?thinkaboutthatlaternowfig- _

“Stop Kanao!” Shinbou ordered. Kanao froze. 

_ Finebyme.  _ Nezuko pounced at Kanao. An iron grip yoked her back.  _ Whatthehell!  _ She raged.  _ Foul play!  _

Her blood ran cold. It never occurred to her that Kame had a head underneath his helmet, much less a human face. The night’s darkness masked most of his face, but she could make out his gritted face and brown eyes.

Angry eyes, as if blistered by the fires of hell. He let go. She gasped.

“Nezuko!” Tanjiro hugged her. “You’re okay! I thought the poison would’ve killed you. Do you still feel sick?”

She shook her head.  _ Don’t worry. I’m fine. _

“The poison was too weak to kill her. She’ll recover.” Shinobu said. They both turned to her. Their hearts jumped.

“I think things have gotten a little bit out of hand.” She stated nonchalantly. “We need to regroup at the Butterfly Estate and talk all of this over. Our goals are the same, so all this fighting is fruitless. As long as I have my answers, I see no other advantage other than cooperation.” Nezuko glanced at Tanjiro. His dropped jaw confirmed her sanity.

_ I’m not the only one seeing this. But, it can’t be happening, right? There must have been some other drug in that gas. _

“S-Shinobu?” Tanjiro’s said, mortified. “Are you wearing Kame’s helmet?”

The helmet fit Shinobu like a C-4 strapped to a cat. She smiled. “Yes. It’s very nice in here. It feels like the world can’t touch me.” She paused.

“Oh? That’s amazing!” she randomly said.

“Who are you talking to?” Tanjiro asked.

“VEGA!” she smiled.

_ //////////////////While Tanjiro was Fighting Kanao//////////////////// _

_ He’s doing it again.  _ She had heard about this tactic from Giyu: The man had entirely focused on Giyu’s sword for the battle. This time, he was gunning for her head. It made predicting his strikes easy, but his physical prowess challenged her. Several shells scraped her skin. Several cuts scraped his; the poison had little effect on him.  _ Even the poison specifically made for humans has no effect. Drat. _

_ He needs a full dosage.  _ She launched herself high into the air.  _ With a sudden burst of speed, he won’t have time to leap out of the way. _

_ My blade is too small to block; it’ll slide through any openings and pierce him. _

_ Total Concentration Insect Breathing: Butterfly Dance, Caprice! _

She sprung at her enemy – sword thrusted forward. He angled his body so that the blade slid over his shoulder.

_ Or he could do that. _

She tried to bounce away. In that split second of escape, he ripped off his helmet and dunked it on her head. Shinobu leaped away with the weird helmet on her head.

_ Huh. Not the worst outcome.  _ She tried to take it off, but it was stuck. A bright display popped up.

_ USER NOT RECOGNIZED. ACTIVATE GUEST ACCOUNT? _

Kame nodded.

_ GUEST ACCOUNT: GUEST_001 ACTIVATED. _

“Hello there, Shinobu.” said the helmet.

_ It’s talking to me?  _ “Are you Kame?” Shinobu asked.

“No. I am VEGA, the assistant A.I to the Doom Slayer’s systems.”

“A.I?”

“Artificial intelligence.”

“Well you don’t feel artificial to me VEGA.”

“I appreciate your compliment. The Doom Slayer has asked that I explain the current situation in which we’re in. He hopes we can reach a truce.”

“Kame? He does speak!”

“He says enough.” VEGA explained.

“But he doesn’t have to be so shy about it. If he has a weird voice trust me, I won’t laugh.” Shinobu teased.

“He hopes you’ll understand the situation – he’d hate to have to kill you.”

“So polite of him.” She Smiled.

“I will explain everything.”

<Several minutes of Intricate diagrams later>

//////////////// //////////////////////

The sun rose over the composite group. Tanjiro covered Nezuko in the usual cave-blanket. Kame was wearing his helmet again while Wisty endured his hangover on Kame’s shoulder. Shinobu happily skipped besides Kame. Kanao and Tanjiro walked side-by-side behind the wagon (for completely tactical reasons).

Kanao flipped her coin. “Why don’t you ride on the wagon?” she asked.

“You said it yourself. I’m not going to get any stronger sitting down. I’ll take every opportunity I get to move forward.” His legs greatly disagreed.  _ I hope we’re close.  _ He winced.

“If you travel with your sister, you’ll have to pull that wagon everywhere.”

“I was just thinking about that. I had this idea for a basket to carry her around in; then I’d just have to carry her around like a backpack, but I haven’t gotten the chance to try it out.” He said.

“That could work.” Kanao agreed.

“Yeah.”

“...” Kanao softly smiled at him.

“…” He smiled back, waiting for her to say something. 

He went first. “Anything else you wanted to ask?”

Kanao flipped her coin. She shook her head.  _ At least there’s more people to talk to now. What about Shinobu? _

“How do you know about Kame, Shinobu?” He asked.

“He attacked a friend of mine a few days ago.”

“That recently?”

“Yes. According to VEGA, it was just to get his blade.” 

_ Right,  _ Tanjiro remembered,  _ VEGA, the ghost possessing Kame’s helmet.  _ “The same one on his arm?”

“Same one.”

“So he’s not part of your group.”

“Yes he’s not. VEGA gave me a basic explanation, but I think we should wait until we get to the Butterfly Estate before asking more questions. There’s a reason why the Demon Slayer Corps keeps a low profile. I would like to keep it that way.”

He nodded. “How much longer until we’re there?”

“Another night.” Shinobu said.

Kame stopped moving. 

“What is it, Sir. Slayer?” Kame gestured to the wagon. “Hmm?” she frowned. 

Tanjiro understood the message. “He wants us all to get in the wagon.”

“All of us?” She glanced at Kame’s rippling muscles. “Alright. Come on in Kanao.” They all got into the wagon. 

Tanjiro’s instincts immediately yelled at him to hold on. Suddenly, Kame tore his way down the path with terrible speed, the wagon in tow.

“He’s this fast?” He gasped, the wind threatening to blow off his haori.  _ Amazing! What were we walking for? _

“Thanks for the ride Sir. Slayer!” Shinobu cheered. “You’re so kind!”

_ That’s not it,  _ he thought,  _ he just wants to speed things up. _

He remembered what Kanao said. About Kame’s hate for demons. About Nezuko. The same Nezuko that hid in her small shade from the sun. His little sister.

_ We’ll prove him wrong. _

**Notes for the Chapter:**

> I realize it's April Fools and that I don't have some elaborate joke set up.  
> ...  
> Happy April's Fools!


	5. Doctor Of The Slayer Part 2

**Notes for the Chapter:**

> Ironically, the shortest chapter so far comes after the longest chapter. Short, but full of decisions.  
> No new spoilers ahead.
> 
> Enjoy.

////////////////////////////////////////////////////////////////////////////////////////////////////

The Butterfly Estate glittered under the setting sun, its myriad facilities rolled like carpet before the main mansion, ready to assist the injured at a moment’s notice. Today was a quiet day, and Aoi could hear Naho’s excited shrieks all the way from the gate.

“Shinobu and Kanao are back!” Naho cheered.

_ Perfect timing.  _ Aoi washed her apron. Shinobu had told her that her mission was a difficult one. It was a relief she had come back in one piece; just in time for dinner at that.

“Welcome back Shinobu,” She bowed before the Butterfly Hashira. “I'm pleased to report that there have been no problems since your abscence.”

“Thank you Aoi.” Shinobu smiled. “Oh, I see you’ve already prepared dinner. Mind if we start eating it now?”

“Of course not. Should I call the others to join in?” Aoi asked.

She pursed her lips. “If they want to come. Come on everyone!” She clapped to the motley crew behind her: Kanao, a green soldier, two strangers, and a white rabbit. Aoi's heart jumped.

“Who the hel-” she blurted.

“Langauge,”

“-heck are they? Allies? Visitors?”

Shionbu gave her an optimistic grin. “It all depends on dinner.”

Aoi gulped.

“Oh, and one more thing Aoi,” she remembered.

“Yes?”

“Could you please bring me that black box we found – that one from two weeks ago.”

_ What could she want with that?  _ “Right away.” Aoi bowed.

////////////////////////////////////////

Back to square one. They all patiently sat around the Chabudai table, Kame's shadow stretching across the relatively small table. The only person missing was Kanao. Tanjiro didn’t know where she was. 

Shinobu welcomingly sipped her tea, her taste buds relished its warm flavor.

“That was quite the trip. Are you sure you’re not tired, Sir Slayer?”

Silence.

Tanjiro and Wisty anxiously eyed the food – a feast of fried fish, rice, and other culinary delights bared before them. Wisty blood-houndedly sniffed his lettuce. “Don’t worry, they’re not drugged this time.” Wisty dove into his lettuce. Feverishly, they all began eating, except Nezuko and Kame.

“Again? Are you sure Nezuko? I can see your ribs now,” She shook her head.  _ Odd. _ “Don’t demons still need to eat?” He asked.

“They can become malnourished within a week. On the 6th day they’ll go rabid and eat anything they can get their hands on.” Shinobu explained. “Admittedly, it’s amazing how your sister is still docile on an empty stomach.” Nezuko rolled on the floor like a bored kitten. “For the moment…”

“Since you are truly my guests now, I should properly introduce myself. My name is Kocho Shinobu. I am the Butterfly Hashira of the Demon Slayer Corps, one of their main seven pillars.”

“The Demon Slayer Corps are an independent organization who have fought and protected the people from the demons for centuries. Our goal is nothing less than the eradication of the foul Demons and the man who leads them. The demons we fight are immortal, powerful, and strange.”

“If what Mr. Vega told me was true,” she pointed at Kame, “you are not from around here – you came from Mars, and your real name is The Doom Slayer.”

Kame nodded.  _ What kind of father names their child that? _ He wondered.

“Is VEGA the spirit in Kam-” Tanjiro paused. “what do you prefer to go as?”

Silence. The Doom Slayer couldn’t care less.

“Is VEGA the spirit in his helmet?”

“Yup! He’s the one who told me about this country called ‘Mars’ and how they fought different types of demons there.”

_ Could he know something about Muzan?  _ “Could I talk to VEGA?” he asked The Doom Slayer.

Rejecting silence.

“Oh my, it looks like he doesn’t want to share.” She giggled.

A large OOMPH pounded against the floor. One of Shinobu’s assistants - Aoi - struggled to drag in a cumbersome box. A hexagonal prism, the device was black all-over and taller than Aoi. Sweat ran down her face.

“I…got…it…” her grip slipped. She flopped to the floor. “It’s…really heavy…”

“Let me help,” He offered.

“NO.” she swatted his hand away.

“You might break your back.”

She frowned at Tanjiro’s fragile body. “I said I’m fine!”

The load suddenly lightened - Kanao had picked up the other end.

“Where were you?” He asked. She held up a bag of medicine. “For who?” she pointed at him. “Really? Thank you!”

“We’ll both help you,” Kanao said.

“…Fine,” Aoi muttered. Together, they lugged it into the room.

“Two weeks ago,” Shinobu began, as Kanao treated Tanjiro’s wounds properly, “In a flash of red lightning, this weird...box... appeared on the estate. I tried to examine it. I could tell it was man-made, but its entire design was alien to me. Then, several days ago, lightning flickered out of the machine. Less than a day later I got a crow from a friend about you.” A curious grin purred at The Doom Slayer. “Would you know anything about that?”

Silence. The Doom Slayer read the big U.A.C initials.

Aoi tried to warn him. “Watch out, it’s – “ He picked it up in one hand. “-heavy.” There was a small hole; he inserted a silvery chip into it.

“PROGRAM INITIALIZING” The air sizzled with awe and energy as the box whirred to life. Steadily, it relaxed.

“Initialization complete. The Tether Tunnel is sophisticated enough to run my program - I have now been downloaded.” The box announced.

“Kame?” Tanjiro gasped.

“No. I am VEGA.” Everyone was shocked – especially Aoi.

“That spirit can possess other things?!” Aoi raged. “What if it infects one of us?”

“I’m sure VEGA’s a nice spirit.” Tanjiro assured her. Kame agreed with a thumbs-up.

“That’s what all spirits want you to think!” she ranted. “Shinobu! Please don’t tell me you’ve associated so rashly with this spirit!? These complete strangers!?”

“Share my faith, Aoi. I trust him. He was very close to me once and didn’t do anything vile."

"H-how close?" Aoi queried.

"He was like a voice in my head," Shinobu teased. Aoi lost  _ her _ head.

“Y-you,” she stutteredly pointed at VEGA. “with h-him.”

Shinobu mischievously grinned. “Yes,”

“It was private,” VEGA added innocently.

Aoi excused herself from the room.

////////////////////////////////////////

Far away from Shinobu’s keen ears, her worried shrieks were only heard by Shinobu’s other assistants. 

“Aoi overreacted again,” Sumi sighed, barely heard over Aoi’s worried.

“again,” Kiyo sighed.

“again,” Naho sighed.

////////////////////////////////////////

“I’m sorry. I shouldn’t have provoked her.” Shinobu apologized for her immaturity. “Now then, since you can talk freely now, would you please introduce yourself to everyone, Mr. VEGA?”

“My name is VEGA.” He corrected her.

“Okay Mr. VEGA.” She joked.

VEGA ignored her. “I am an artificial intelligence called VEGA, originally tasked to oversee a facility on Mars. Now I assist the Doom Slayer in his mission against the demons.”

“Where is Mars exactly?” Tanjiro asked.

“It is the 4 th planet from the Sun.” he explained.

“How far is a planet?”

“A planet is not a distance. It is a celestial body in Space.”

“A planet is - ouch.” He winced.

“Sorry,” Kanao softly spread a medicinal lotion over his damaged face.

“A planet is located in a country called Space?”

“Space is a vacuum.” said VEGA.

“He briefly told me about this before,” Shinobu jumped in. “Space is a floating area – a void outside of our country. Mars is found in this area.”

“So Earth is located in space. Where is Mars located?”

“In Space,” 

“So Space is a place where Mars and Earth are. And you just came here?” 

“No. Space, in astronomy, is a description for a free, unoccupied region where nothing exists. No air, earth, or light - a vacuum.” VEGA explained. “A planet is a massive conglomerate body of elements and molecules that float in space. That’s why it’s referred to as a celestial body. Earth is a planet, and it is the one that you live on at this very moment. Both Earth and Mars are in space. The same holds true for the myriad of other planets that also reside in Space. Mars is a planet near Earth, and Mars is where the Doom Slayer fought the forces of Hell.”

Town-boy Tanjiro and Doctor Shinobu perfectly understood this brief description of infinity.

“So Space is a lake?” Tanjiro asked.

“It sounds more like a sea.” Shinobu added.

Had VEGA not been programmed to wait hundreds of years to process experimental data, he wouldn’t have had the patience to keep explaining the topic.

The Doom Slayer didn’t share this enthusiasm. He ordered VEGA to stop.

“We will continue this another time.” VEGA said. “For now, we should discuss all our current goals. The Slayer is planning to leave.”

“When?” Tanjiro was baffled.

“After this conversation. To hunt demons again.”  _ So soon?  _ Tanjiro thought.

“You sure you don’t want to stay here longer? We could get to know each other better.” She suggested. 

Silence. Experienced with silent types, Shinobu didn’t ask for anything more. She wistfully nodded.  “Understood. I will continue my duties as the Butterfly Hashira.” She turned to Tanjiro. “You will stay here for the time being.”

“Thank you for the offer, but we can’t just live off of your work. It’s not honest.”

“That wasn’t a suggestion.” She gleefully sipped her tea again. “I’ve never had the chance to examine a demon’s physique in such liberating circumstances before.” Nezuko hid behind Tanjiro. “Don’t worry, it won’t hurt.”

“That’s…nice.” An idea sprang into his mind. “That means you can teach me, right? Like how you taught Kanao!” Tanjiro bowed before her. “Please, train me.”

She shook her head “No. At least, not at the moment. You still haven’t fully recovered, and I have to make sure Kanao’s ready for the Demon Slayer Entrance Exams.”

Kanao flipped her coin. Tails. “I can train myself.”

“Awfully talkative recently,” Shinobu playfully smirked, “has something changed?”

Kanao shook her head.

“Nevertheless, I still have a serious responsibility as chief doctor of the Demon Slayer Corps, and as Kanao’s master. I cannot neglect those responsibilities.”

“I’m sorry,”

She smiled. “For the moment you’ll have to wait. Fortunately, I am not the only Demon Slayer in existence. I’m sure there are others more capable or free than me to oversee your training. For now, we just have to wait for you to fully recover.”

“Unless…” She mused. “I trained the demon.”

The bubble of calm burst. Everyone stared at her. Tanjiro’s heart skipped a beat. Nezuko’s eyes shot open. Wisty glanced at the Doom Slayer. He wisely hid underneath the table.

She snickered at their surprised faces. “Well, it would be more efficient. She already has increased strength, she isn’t as injured as Tanjiro, and…and…” she stifled. “she...” Shinobu couldn’t hold it in anymore.

Suddenly, Shinobu uncharacteristically laughed. Not a secretive or sly laugh, but a ge - nu - ine, gut-bursting laugh that choked tears out of her eyes. She kept laughing and laughing for several minutes. “S-sorry,” she teared. “It’s just too ridiculous – a demon becoming a demon slayer.”

“I’ve heard of Demon Slayers becoming Demons, but the other way around? Ludicrous.” She said.

Silence. The Doom Slayer glared at Nezuko, his fingers hovering over the trigger.

Everyone in the room fell silent.

Slowly, Nezuko stood up and glared at Shinobu. Not with hunger or hate, but determination.

////////////////////////////////////////

_ Why am I doing this?  _ Everyone’s eyes drilled into her face – especially Kame’s. Her insides felt like jelly; bouncing around every time her legs wavered. She wanted to shrink into a dark box and hide from it all. and why shouldn't she? Other demons terrified her. The sight of one sucked her back through the same vortex of emotions she had felt on that mountain: Fear, frustration, confusion, helplessness.

She didn’t have to do this. Here she could stay safe (relatively). Protected.

_ But Tanjiro’s going to become a Demon Slayer no matter what gets in his way, just for my sake. I can’t let someone else get hurt again because of my weakness.  _ She steeled herself.  _ Because of that, I’ll train. So that Tanjiro and I can find a cure and get vengeance on the Demons. _

_ Together.  _

Nezuko cupped her hands together and respectfully bowed before Shinobu.  She didn’t remember much about her past life, but she remembered this was considered a sign of respect. 

Shinobu's eyes glimmered. “Interesting…”

Nezuko could feel The Doom Slayer’s hellish aura. It set the whole room ablaze. Nezuko's skin blistered from the heat.

_ And, _ she gulped, _ and I’ll prove him wrong.  _ She didn’t step down. Her mind was made up.

The Doom Slayer had heard enough _.  _ He picked up Wisty and, BANG, slammed the door shut behind him.

“Hold on,” Shinobu dashed after him.

Without warning, Nezuko crumbled to her knees, a sluggish numbness pumped through her veins. Her stomach growled, and her head felt drowsy. _T_ _ he hell? _

She hadn’t eaten in days - her instincts knew that normal food wouldn’t be enough for her anymore. Humans were more than enough of a feast, but she resisted the temptation to eat them.

It was as if, to compensate, her body needed to sleep. A very, very large amount of sleep.

The world slipped out of her senses and went dark. The last thing she felt before she fell asleep was Tanjiro’s hand catching her as she fainted.

////////////////////////////////////////

“Private radio established. This Tether Tunnel is designed to create a connection between this world and ours, but it only works one way. If I work within the minimum requirements of my systems, there is enough Argent Energy to run this device for 10 years. It is strange why this device was even conceived, since the Well is no longer operational. Dr. Hayden has most likely re purposed the Crucible as a substitute.“ VEGA concluded

The Doom Slayer clenched his fist.

“Are you sure you wish for me to remain here?” He asked. “I will not be able to contact you beyond this mansion.”

Silence.

“Understood. I will assist Shinobu however I can. Remember to bring back samples to help my investigation of the demons.”

"Safe travels," VEGA added before he ended the call.

A petite hand grabbed the Doom Slayer.

“I know how you feel,” Shinobu started. “Working with demons - It feels like you’re betraying everything you ever fought for.”

The Doom Slayer brushed her aside.

“Still, there is an opportunity here that I cannot refuse. With proper training, humans can fight Demons on near-equal footing. Can you imagine how effective it would be if a demon used such skills?”

Silence.

“I understand what could happen if anything goes wrong. But it is worth the risk, I assure you.”

The Doom Slayer shoved Shinobu to the ground. He had heard that excuse many times before. Demons were soulless beings. No matter the time or place, their silvery tongues and claws brought everything less than false promises, lies and madness.

His fingers hovered over the trigger. He should just kill it now, before she spiraled out of control.

Wisty nudged the Slayer’s head to Tanjiro. He could still see Tanjiro as he desperately tried to shake Nezuko awake. Tears in his eyes, but also, something else.

The Doom Slayer marched away. He wasn’t sparing her, he was giving her a chance.

“Bye mister, stay safe,” Sumi waved him goodbye.

“Stay safe,” Kiyo waved.

“Stay safe,” Naho waved.

The Doom Slayer marched away from the glittering mansion, leaving behind Tanjiro and Nezuko on their own paths.

No doubt that they would cross again

////////////////////////////////////////

**Notes for the Chapter:**

> Don't worry. The Doom Slayer is not going to be out of the story for long. The focus just shifts to Tanjiro and Nezuko for a while, with tidbits of the Slayer's crusade.   
> Hope you enjoyed the story.


	6. Testaments of Tanjiro Part 1

**Notes for the Chapter:**

> Sorry for the long hiatus, I've had a busy past few months!  
> Hope this chapter is worth it!  
> No new spoilers.

////////////////////////////////////////////////////////////////////////////////

_Tanjiro’s Diary_

_Day 1_

_I’m logging everything that happens now in this diary, so you’ll be up-to-date once you wake up. Plus, I need to practice writing with my left hand (sorry for the sloppy handwriting)._

_Kame, The Doom Slayer - neither feels right to say, left yesterday. According to VEGA, he’s going to find a way to stop the demons._

_I think he’s going after that man – Muzan Kibutsuji._

_He let us borrow VEGA in case anything weird happens. He’s a nice spirit. Smart too, he knows a lot about everything: Science, history, Japan, and Christianity. But his ‘Tether Box’ is heavy and can’t move on it’s own, he has to be dragged everywhere. It’s nice to have him around (Aoi disagrees)._

_Shinobu promised she’ll figure out why you’re in a coma. For now, you’re okay. Thankfully._

_My hand is already cramping. I’ll have to stop for today._

_I hope you wake up soon._

_Prayers,_

_Tanjiro_

////////////////////////////////////////

_Tanjiro’s Diary_

_Day 7_

_I’ve finally started training today, Shinobu gave me a list of activities to do: Running, sit ups, push-ups (they’re a lot harder with one arm), the like. Nothing serious yet. Oddest of all, Shinobu gave me workouts to focus on my breathing. It's the key to learning Total Concentration Breathing, an essential skill for Demon Slayers that empowers certain techniques with immense power. That must be why Kame’s so strong._

_As for your condition, Shinobu hypothesized that you fell asleep because you hadn’t eaten anything for a while (I told you so!). Your body is regaining energy by sleeping, something unique to you apparently. You’ll be fine, but she doesn’t know when you’ll wake up. And when, if, you do, how much time will have passed by then?_

He paused, his hand wavered over the fresh paper, hungry to write more.

_You really wanted to become a Demon Slayer. I could tell. But, I’m your big brother. I can’t let my little sister do something so dangerous. Maybe it’s better if you didn’t wake up yet, like a princesses from those fairy tales: Waking up to a world where everything is normal again, where you’re human again. I’ll even find a charming frog for you to kiss._

He glanced at Nezuko. Under the full moon’s heavenly gaze, her skin sheened a corpsely pale color. Under her blanket, she sleepily curled to the side on the spacious bed, a bamboo muzzle strapped to her mouth. He crossed-out the previous paragraph and instead added:

_If you wake up with a muzzle, blame Shinobu. She doesn’t want anyone to cut themselves on your teeth. They’re really sharp._

He sighed. 

_I hope you wake up soon._

_Prayers,_

_Tanjiro_

////////////////////////////////////////

_Tanjiro’s Diary_

_Day 8_

_I had a nice dream last night. I was lying on the ground, frozen. Our family: mom, dad - everyone, was praying for me, and crying. I couldn’t hug or speak to them, no matter how hard I tried, and I felt no bitterness or hate from them. Only hope, as they wished me the best of luck._

_I pray you’re having the same kind of dreams._

_Prayers,_

_Tanjiro_

////////////////////////////////////////

_Tanjiro’s Diary_

_Day 14_

_I had another dream, similar to the last one, except now everyone was stacking charcoals’ next to me, repeating how I had to save you and how they’re sorry they couldn’t be there with me, the pile of charcoal rising with each uttered sentence. It soon collapsed, then I woke up. I think they were trying to tell me something. I don’t know what it was yet._

_As for how things are going, they're great. Life at the Butterfly Estate is surreal: Built upon a rolling hill painted by warm colors from a lucid dream, each building radiating a homely aura. The Butterfly Estate is the main medical ward of the Demon Slayer Corps, so there are patients and Kakusha’s - the labor force of the Demon Slayer Corps – about, yet the place is usually quiet. It’s due in part to the layout of the estate, and due in part to the expected hazards of fighting demons. As Aoi put it, Demon Slayers either die a horrible death, or they live long enough to get treated at the Butterfly Estate._

_I don’t doubt her. I’ve seen patients with cracked ribs, broken bones, spilled guts, all clinging to their life and duty. No wonder everyone awes at my scars – it’s a miracle I’m alive._

_I help around. It’s nothing worthy of making me a doctor, just little chores like chopping wood and getting medicine._

_Shinobu checks on you every day. She’s been working on a way to wake you up sooner, since it could be years before your coma ends. I’ve been practicing my sense of smell recently, I can smell this spike in frustration every time she leaves your room. She’s used to killing, not caring, for demons._

_My hand cramped again. I’ll stop writing for today._

_Prayers,_

_Tanjiro_

////////////////////////////////////////

_Tanjiro’s Diary_

_Day 21_

_Some things have changed since the last time I wrote. A few days ago, Shinobu left your room, frustrated; a common sight at that point. Then, suddenly, the lightning of an idea struck her. Her eyes glazed with inspiration. Soon after, VEGA was moved next to Shinobu’s study, and he’s been there ever since. She frequently talks to him now, even bringing him inside when it rains. Now when she leaves your room, Shinobu doesn’t smell as frustrated anymore. Aoi ranted that VEGA would possess her, but her worries fell on deaf ears._

_Unfortunately, VEGA can’t scan your body without the Doom Slayer’s help. I’ll ask him to help when he comes back._

_Prayers,_

_Tanjiro_

//////////////////////////////////////// 

_Tanjiro’s Diary_

_Day 28_

_I smelled him before I saw him – The Doom Slayer. He returned today, carrying a large sack that writhed violently, as if it were stuffed with stray cats. He headed to Shinobu’s study:_

////////////////// _FLASHBACK_ //////////////////

He followed the Doom Slayer to Shinobu’s room.

“Hey, knock first.” He didn’t, catching VEGA and Shinobu by surprise. The latter’s eyes shot open, as if being caught with a notebook was a crime. VEGA sat opposite to her.

“Welcome back, Slayer.” VEGA began. The Doom Slayer shut the shutters.

Shinobu slid her notes into the nearest drawer. “Hi!” She said with regained posture. “Nice to see you again. How have you been?”

Silence. With little care for the contents within, he emptied the bag.

Three, live, screaming demon heads tumbled onto the ground. Tanjiro’s weak stomach did a backflip.

“Oh my,” Purple eyes sadistically flickered. “Thank you! Most people just kill them before I can study them properly.”

“Connecting...Using Praetor camera to scan now,” VEGA’s voice was drowned out by the screaming heads.

“END US!” One pleaded.

“SHSHSHSHSHSHSH” The other grinded, his teeth spinning like sawblades.

“WE WON’T EAT TEENAGE GIRLS ANYMORE. WE’LL GO ON A DIET!”

“YEAH! GUYS ONLY!”

“SHSHSHSHSHSHSSH”

The Doom Slayer’s foot shut them up with a hollow CRUNCH.

“W-what did we do to deserve this…” The first sobbed as he slowly regenerated.

“Scan complete. Amount of demonic foreign substance at standard levels. High concentration of human blood.”

“He caught three demons?” Tanjiro asked.

“No. Demons don’t work in groups. This one must have split himself into three separate bodies, that’s why they’re all identical to one-another.”

“They can do that?” He awed.

“After consuming enough humans, demons can develop unique abilities known as Blood Demon Arts. But this one’s lame. What’s the fun in talking to yourself?” She shook her head. “Fortunately, that means I only need one head for my studies...” She flashed her sword, Wisteria poison dripping from it's tip. “Now, which one of you was the talkative one?”

All three heads promptly shut up.

“Good heads!” She patted them. “We’ll get along just fine!” The Doom Slayer glanced at VEGA.

Silence.

“Understood. Shinobu, do you have anything new for the Doom Slayer?” VEGA asked.

“Oh, me? Well, not yet. ~But!~” she promised. “If you come back in a few weeks, it’ll be ready!”

The Doom Slayer had already left the room (“Not taking any shits from a woman. I can get behind that!” One head drawled before he tasted Shinobu’s foot).

Tanjiro followed him. “Hey! Doom Slayer!” Despite his past trials and errors, he was still just as eager to strike up a conversation. He tried to break the ice. “How’s Wisty?”

Silence. He gave him a thumbs up.

The Doom Slayer stopped at Nezuko’s room. “Again, you should knock first. Especially since it’s a girl’s bedroom.” Again, he didn’t.

Far away from the streams of sunlight trickling through closed curtains, Nezuko slept. If not for her cyclic breaths, she could have been mistaken for a misplaced corpse. Wisty’s ears drooped. The Doom Slayer glared at her. No suspicious movements. 

“She’s in a coma.” Tanjiro explained. “Since she hasn’t eaten any humans, she needs to sleep to regain energy, which might take years. Your suit’s camera could help figure out how to wake her up. So could-” The Doom Slayer slammed the door shut and left. _Figures. He was never interested in helping Nezuko._ Tanjiro sighed. _At least he hasn’t killed her yet. I’ll just have to keep trying._

“Bye Mr. Slayer,” waved Naho, Kiyo, and Sumi as The Doom Slayer marched back into demon-ridden Japan. “Stay safe.” They repeated in their triplet pattern. “Come back soon!”

//////////////////// _PRESENT_ ////////////////////

Tanjiro finished his diary with words of optimism.

_We’ll prove him wrong, Nezuko. Sleep well._

_Prayers,_

_Tanjiro_

////////////////////////////////////////

_Tanjiro’s Diary_

_Day 44_

_Sorry I haven’t written in a while. Shinobu went on a mission with the Water Pillar several days ago. His name was Giyu Tomioka. I talked to him. Quiet and cold - like a calm ocean. A bit odd, but he was a nice person to talk to. What struck me the most was that he wasn't that much older than me. Before they left, Shinobu tripled my workout and then some. The increased training is great, but it makes every word a pain to write. I have to tie the pen to my hand if I want to scratch a word._

_When she’s not practicing, Kanao watches me train, correcting any flaws in my style. She, too, can’t be much older than me. In retrospect, most of the active Demon Slayer I’ve met are never older than 30. If they are, they’re usually teachers or have already retired (Except the Doom Slayer. Something tells me he’s definitely older than 30)._

_Otherwise, life Is still good, thankfully._

_Crap. Cramp. Bye._

_Prayers,_

_Tanjiro_

////////////////////////////////////////

“You’ve been busy,” The swordsman’s shadow stretched across the snow-peaked mountain, stretched amidst whistling trees. Giyu’s ocean eyes gazed into the darkness, still noticing the dark rings under Shinobu’s eyes. “The makeup does a horrible job of covering it up.”

“Of course you’d be the first one to comment on a girl’s looks.” she silently cursed her weak complexion.

“Anything the matter?”

“Well, I’ve been getting more and more patients lately, and the Kakushi are stretched thin. It’s been a chore to get everything done, more so than usual.”

“They should make the entrance exams harder.”

“Or build another Butterfly Estate.” Like the wind, her jest echoed throughout the forest. Giyu frowned at her. “Oh, you could at least pretend to laugh,” She shook her head dismissively, “this is why no-”

“Why what?” Giyu’s frown deepened.

“-nothing.” She didn’t want to pull that pin yet.

He shrugged, changing the subject. “What about him?” He caressed the grip of his new blade, drowning out silent footsteps.

“Be more specific.” she politely smiled. Giyu always did this - talk as if she knew exactly what he meant. She did, but his curtness still irked her.

“The green soldier. Has he been dealt with?”

“Yes. He was just a man who dedicated his life to killing demons. He won’t cause the Demon Slayer Corps any more trouble.”

“Good,” The demon pounced at his neck.

_Total Concentration Water Breathing 1st form: Water Surface Slash._

The Demon’s ashes scattered with the wind, nothing more than a harsh whisper. 

“Oh my. He didn’t put up much of a fight.” Shinobu sighed, “We shouldn’t have had to come.“

“A waste of time. If the standard Demon Slayer can’t deal with something like this, I have many concerns.”

“To be fair, stealthy demons are the most tedious to deal with. Oh!” she lit up. “If we taught the Demon Slayers to talk less, then they'd avoid ambushes better! You could teach them!” She teased.

“Too time consuming. Improved tracking skills would be the better way to counter demons’ stealth. Like that boy, Tanjiro. With only his nose, he estimated the number of demons my blade had felled. I’ll ask Urokodak if he’s not encumbered. It might take a while, I prefer to visit him in person.”

“Isn’t it because you’re too scared to use Kanzaburo?”

“...”

“Silence can speak more volumes than words.” She tutted.

He sheathed his sword. “Is there anything else that’s bothering you?” He asked.

She recalled her heretical idea to train a demon, the specifics regarding The Doom Slayer, and her dealings with a foreign spirit. “Nope! Everything’s fine and dandy!” She assured him with practiced words.

////////////////////////////////////////

_Tanjiro’s Diary_

_Day 45_

_Some…disturbing news. There’s nothing important here, so you’re free to skip this entry. I’d recommend it, actually. I only wrote this to make sure I’ll never forget today._

_I went to Shinobu’s room to ask VEGA if he had any ideas on how to wake you up. It wasn’t anything I hadn’t heard before, except for his suggestion to feed you human flesh. He even told me how to efficiently prepare a human sacrifice._

_That option is out of the question._

_Then I made the mistake of asking VEGA what happened to the other demons Shinobu had kept. I hadn’t heard their screams in a while._

_They were in the cupboard. Inside, two, air-tight jars, each stuffed with a familiar demon head. The third jar had only fine soot in it - the demon had died from starvation. It was an experiment to see if demons needed air to live. Their malnourished faces concluded Shinobu’s theory._

_Killing is unforgivable. These demons deserve to be punished, not tortured. So, I let the jars out into the sun._

_Shinobu came back today. If she noticed anything different in her room, she didn’t mention it. It’s hard to imagine someone like her doing something like...that._ _In a weird way, she reminds me a bit of The Doom Slayer. Both hate demons to the point they’re willing to do anything to kill them, even if it means killing themselves._

_I don’t want to go down that path where I have to sacrifice my humanity to fight demons, and I won’t. I will fight demons, but I will still be Tanjiro Kamado at the end of it._

_And if you’re truly going to become a Demon Slayer, please don’t stop being Nezuko._

_Prayers,_

_Tanjiro_

////////////////////////////////////////

_Tanjiro’s Diary_

_Day 55_

_So, VEGA can do a lot more than talk or scan things. He can also summon things! Today, he suddenly lit up in a blue hue, energy cackling out of his box, and was struck by a lightning bolt! Luckily, he was outside when it happened. According to VEGA, it was a gift for the Doom Slayer. He couldn’t tell what it was though. I didn’t know The Doom Slayer had friends._

_The event riled up Aoi. Now she guards Shinobu's study throughout the night, VEGA close to her as she sleeps. Shinobu failed to persuade her otherwise._

_..._

Should he mention the nightmare? He could still recall it vividly:

Towering buildings scraping the sky, crumbling, crashing to the ground that danced with guns and claws. A rip through space and time, to a crumbling sanctum nestled within crimson alpines, filling him with unfamiliar nostalgia.

He shook his head decisively. No. He was writing to soothe Nezuko, not alarm her. He could take it. He continued writing as per normal.

...

_I hope you wake up soon._

_Prayers,_

_Tanjiro_

////////////////////////////////////////

_Tanjiro’s Diary_

_Day 62_

_Shinobu just received her package today, the one she had promised The Doom Slayer a while back. She wouldn’t let anyone see it, not even VEGA (though current circumstances made it easy)._

_I wonder whose gift will be better._

_Prayers,_

_Tanjiro_

////////////////////////////////////////

_Tanjiro’s Diary_

_Day 70_

_The Doom Slayer returned today, a new attachment on his shotgun (must have been VEGA’s gift) and a fresh bag of demon heads’ in his other hand. Wisty curled up on his shoulder, spoiledly plump. Shinobu asked him to wait as she got him his present…_

//////////////////// _FLASHBACK_ ////////////////////

“What does this do?” Naho poked the odd attachment: a new barrel on the shotgun, now with a green cylinder that primed unique shells for firing.

“Does it shoot ice?” Sumi asked.

“Does it shoot fire?” Kiyo asked.

The Doom Slayer tossed a pebble into the air. He fired a sticky bomb at it; their ears rang from the immense explosion.

“Yay!” Naho cheered. “Again, again!” another rock. STICK. BANG.

“Maybe do this somewhere else,” Tanjiro coughed.

“Found it!” Shinobu interrupted their impromptu fireworks display, the silk-wrapped gift in her hands.

“Sorry for the wait. The swordsmiths aren’t used to making such weapons, but I knew nothing else would suffice.” Gently, the Doom Slayer unwrapped the gift.

A double-barrel shotgun. Large, with a silvery luster to its barrel and a shiny finish to its oaken stock.

“The barrel’s made out of Nichirin steel - the same alloy your sword is made out of. I also have a box for the ammunition, including some Nichirin shells. You’ll still need to use the Nichirin shells to seriously damage demons, but I’m sure you’ll manage.”

Battle-hardened hands glazed the weapon, caressing it with orgasmic reverence, packaged with the imminent smell of red-hot lead. Wisty’s fluffy rear twitched eagerly.

“Take it as a sign of gratitude.” Shinobu bowed. “While you’re here, you should enlist with the Demon Slayer corps. It shouldn’t be too hard to register you properly, if you took the time-” The Doom Slayer had already loaded the gun and was leaving, at a speed identical to joyful skipping; a vigor matched by trigger happiness.

“Oh well,” She sighed. “He certainly liked the gift.”

“He does have an affinity for guns.” Tanjiro added. “Aren’t you worried? Since he’s not with the corps, would they…?”

“Hunt him down?” Shinobu finished. “I haven’t told the other’s about him yet. He’s not a demon, yet he’s not entirely human either. He’s on our side, yet he openly does whatever he wants. If the Demon Slayer Corps found out about him as a renegade, not as a loyal member, they’ll of course want to question him. When that happens,” she reflected on her fight with the Doom Slayer. “Tanjiro, any chance he could change his mind?”

He shook his head. “No. He likes to do his own thing.” Shinobu agreed.

“I’ve heard some rumors about his feats going around. For now, they’re just rumors. One way or the other, he’ll have to butt heads with the Demon Slayer Corps. It’s up to him how hard he hits.” she resigned.

“Tanjiro, please come check in with me tomorrow. I’ve got something I want to try; I believe you’ll be very interested in it.”

“What is it?”

“Until tomorrow, it’s a secret!” She grinned. She returned to her study as quickly as she had brought it up.

////////////////////////////////////////

_Tanjiro’s Diary_

_Day 71_

_Ohmygoshohmygoshohmygosh._

_YOU_

_WOKE_

_UP_

His hands quivered with excitement. He took a few moments to breathe before he kept writing.

_Well, not really. Otherwise, I wouldn’t have to keep writing this diary. Shinobu injected a special Wisteria stimulant to wake you up, and you did, even if it was for a moment._

_I know it sounds like a bad idea – using a Wisteria-laced medicine on a demon, yet Shinobu assured me it wasn’t a lethal dose. The medicine was like a bucket of cold water: it would shock your body awake and get it working (hence why you leapt out of the bed. Shinobu promised she’ll administer a smaller dose next time). Unfortunately, your body was working on an empty stomach, and you fell asleep again. A longer-term medication is needed. This is a step closer towards success!_

_Hey! I didn’t get a hand cramp this time! Another achievement! Yay!_

_Prayers,_

_Tanjiro_

////////////////////////////////////////

_Tanjiro’s Diary_

_Day 75_

_Today’s my first day practicing with a sword. It wasn’t a Nichirin sword, but it still had a sinister edge nonetheless. Shinobu instructed me to practice 400 consecutive, overhead strikes. I barely made it to 100 before my grip stuttered, I didn’t even cut anything with it._

_When Kanao rehearses the basics, I try to mimic what she’s doing. Her technique is strong in both form and power (Maybe even more so than Shinobu’s blows). It’s embarrassing, comparing the vast differences in strength, but it also pushes me to train harder._

_Speaking about Kanao, I’ve noticed something odd about her. She helps around at the Butterfly Estate, she trains, then she finds a place to stand and...stands. If no one needs something from her, she’ll stay there the whole day, staring at butterflies. It’s like she doesn’t know what to do with herself. Is killing demons all she’s known? I would ask her, but she really doesn’t like to talk unless it’s necessary. Plus, she’s focused on training for the Final Selection - basically the entrance exams that determines whether or not one can join the Demon Slayer Corps._

_Maybe after the exams I’ll talk to her more._

_Prayers,_

_Tanjiro_

////////////////////////////////////////

_Tanjiro’s Diary_

_Day 80_

...

Blank. The page was blank, unlike the deafening headache rocking his mind. They occurred sporadically and randomly; this would be his third major headache since the demon attack. Since The Doom Slayer had, somehow, healed him. Only now he questioned his own stupidity with a slap to the face – a professional doctor was right next door. It was late, though. Resigned to ask her tomorrow, he flopped asleep onto his own bed.

...

_“Good night Mom.” Tanjiro tucked her into bed. “Sleep well. And if you need anything, just call me.”_

_“Are you the mother now?” she giggled._

_“Just…rest. Tomorrow, I’ll see if they have any medicine in town.”_

_“You go to bed too.” His honest heart didn’t reply. “Good night, Tanjiro.”_

_“Good night, mom.”_

_He settled everyone else into bed, soon falling asleep, coddled in layers of warm blankets and family warmth. Except him. He grabbed the axe and waited in bed, ears listening for any danger._

_Slowly, the cool embraces of lethargy cuddled him as the hours ticked by. His eyes shuttered, and the cold pushed his worries aside._

_A knock from the door. He gasped. Had he fallen asleep? Whoever it was, he hadn’t heard their footsteps. He waited. The door was knocked again. He waited, hoping they would think it was an empty house. They didn’t, and the knob began to turn..._

_Tanjiro hastily opened the door._

_“Hello.” The devilishly-dressed stranger said, making it seem like Tanjiro was the one rudely entering his house._

_“Hi,” He made the mistake of looking directly into the man’s cat-sharp eyes. They were predator eyes, boring deep into his heart. He shifted his focus to the man’s hat._

_“Going out to cut some trees?” The man’s gaze curled around Tanjiro’s right hand, the axe frozen to his palm. He had fallen asleep._

_“No.” He changed the question. “Aren’t you cold? The weather’s freezing tonight.”_

_“My health won’t suffer. Sorry if I alarmed you. I was merely interested in this house.” A sudden interest clouded his face. He no longer stared at Tanjiro, but at an incorrigible past. “Nice earrings.” The words came coated in poison. He nipped one of Tanjiro’s earrings, fingering the white card in between his nails, pinching the stylized red sun. “Who gave you away, I wonder?" He muttered. “ I suppose it doesn’t matter now.”_

_The moment flashed before him, their screams vibrating his skull._

_The moment he lost his entire family, soon overlaid by the alien visions he had experienced recently. They melded, then…_

/////////////////////////

He awoke in a cold sweat, darkness still lingering outside. He made up his mind.

...

He tip-toed past Aoi – shivering in her sleep at her self-assigned post, but without VEGA. Quietly, he got her a blanket before knocking the door.

“Come in,” Shinobu replied. He came. “Oh, good morning.” Dark-ringed eyelids forced themselves open.

It was pitch black outside. “Morning?”

“It is exactly 3:01 AM.” VEGA explained. 

“What are you doing up so late?”

“Studying.” She stretched. 

“Hashira train?” Having heard rumors about their immense power, the thought had never crossed his mind.

“We train our bodies however we can. For me, that means improving my poisons. Did you know it takes only 50 grams of Wisteria poison to kill the standard demon?” He didn’t. “I plan to make that 1 gram.”

“And VEGA helps you with this?”

“Yes. He knows quite a lot about biology. He helped with the stimulant for your sister, otherwise I wouldn’t have found the perfect mix of amphetamine and Wisteria for the drug.”

Tanjiro perfectly understood her lingo. Shinobu could tell. “Basically,” she simplified. “VEGA’s a great teacher.”

“Additionally,” VEGA continued. ”The experience reveals more possible demon weak points. The Doom Slayer will find this information instrumental to his crusade. Thank you Shinobu.”

“No, thank you!” she bashfully blushed. “Now, was there something you wanted to ask?”

“R-right. I…I” Shame stopped him. It was only a rare dream, after all. No need to get anyone else involved. Besides, he was the eldest son. He was born to deal with things like this. He asked something else. “I was just wondering, how close are you to permanently waking up Nezuko?”

He had struck a sore spot. Shinobu tsked. “Well, the stimulant proved my hypothesis: Nezuko is sleeping to regain energy. Great to prevent her from eating people, not great for her being active. Something has to compensate.”

She sighed. “I’ve tried using blood from other animals, but it’s not enough. Anything plant-based and her body rejects it. I could use blood donors, but that would mean telling the rest of the Demon Slayer Corps about her.”

He didn’t need to imagine the consequences, talking to the patients at the Butterfly Estate had done that for him. Tanjiro hated secrets, but this was a necessary one: the Demon Slayer Corps was built upon a foundation of hate and loathe towards demonkind. They wouldn’t acknowledge Nezuko’s innocence.

“Maybe after she proves her usefulness, maybe then I could ask for a blood donor.” she shook her head. “No. Until then, I can’t risk it. Only after I’ve finished this.” She waved to the mounds of papers and failed test tubes around her. “It’s just a matter of trial-and-error now. Mostly error.”

An idea struck him. “What if you fed her charcoal?”

Silence. Maybe it was too stupid of an idea to be talked about. Maybe she was too tired to register what he had just said.

“It sounded better in my head.” He broke.

“The idea isn’t entirely unfounded. A friend of mine is into cooking, I remember her trying out a new recipe: blueberry pancakes covered in charcoal.“

“What did it taste like?”

“Whatever charcoal tastes like, I didn't try it.”

His tongue shuddered. “Gross.”

“It’s digestible.” She pursed her lips. “Charcoal is also used to absorb poison in the human body, preventing digestion. Demon digestion is many times more potent than humans, that could be why the medicines' I’ve tested wear off so quickly. With charcoal, larger doses could be administered. Or maybe not. It wouldn't hurt to try. I must be tired to even consider this,” She muttered her last words.

“Well, it’s best that we both go to bed now and…Tanjiro?” Tanjiro staggered, invisible pistons squeezing his brain into paste. He clutched his head, the visions swamping his head again.

Coincidentally, VEGA began to flicker with energy. With a thunderous BOOM, the empty sky struck VEGA with a lightning bolt strong enough to make Zeus jealous. The immense power shook the room. Then, silence, save for Aoi’s distressed yells outside. Tanjiro pulled himself together.

A massive hole in the roof had been torn. Other than knocked over books, desks, and paraphernalia, everything was fine. Nothing was on fire, yet a fine layer of soot surrounded VEGA.

“Another package has been sent for the Doom Slayer.” VEGA announced. “Sender: Samuel Hayden.”

VEGA had never described the sender before. “Is there anything else?” Tanjiro tentatively asked.

“One message.” VEGA read it, his voice taking a gritty, deep tone. “‘Don't waste your ammunition.’”

////////////////////////////////////////

_Tanjiro’s Diary_

_Day 80_

_VEGA is not allowed inside of Shinobu’s room anymore. Lightning bolts occur every time he summons something from his world, no one knows how many more times it’ll happen. He has to stay in the courtyard for everyone’s safety. Poor VEGA, at least he can't feel the cold. Poor Aoi too – she’s scared of being caught off guard again. She still watches VEGA, always finding the time to do so out of her busy schedule. Everyone at the Butterfly Estate is like a family to her, I can understand her concern._

_They should talk more, maybe they can work something out._

_Prayers,_

_Tanjiro_

////////////////////////////////////////

_Tanjiro’s Diary_

_Day 94_

_Shinobu’s stimulant worked this time! The dose wasn’t enough to wake you up, but your body became more active. You’re not as stiff as a corpse anymore. You actually sleep-walked! Sleep-walked! Charcoal actually helped! You can count on the Kamado's to know about charcoal._

_Shinobu said the full thing will be ready in a few weeks. I can’t believe it! There will probably be a lot of problems to deal with once you wake up, but we can figure it out as we go. For now, I’m just glad you’ll wake up soon, even if it isn’t under the sun_

_Prayers,_

_Tanjiro_

////////////////////////////////////////

_Tanjiro’s Diary_

_Day 101_

_A strange boy named Zenitsu visited The Butterfly Estate today. He’s the current apprentice of the former Lightning Hashira. His master wanted to check if he was okay. Apparently, Zentisu had been struck by lightning, and his hair had mysteriously become yellow. No, I’m not making this up. He became blonde from an arbitrary lightning bolt._

_Zenitsu kept whining and bawling how he’d never impress women with his piss-colored hair. He even tried ripping out some of my hair to use as a wig. He wouldn’t calm down, until he saw Shinobu._

_He was a different man. Like a statue chiseled in ecstasy, he froze as Shinobu examined his body, his lips trembling. He later asked me if Shinobu was my sister._

_I hope you never run into him, Nezuko._

_Before they left, I asked his master if he could train me. He said he was too old to take on another pupil, but he admired my spirit._

_Spirit isn’t the only thing I need to push forward. I will do whatever it takes for you to walk in the sun again._

_That’s a big brother’s promise._

_Prayers,_

_Tanjiro_

////////////////////////////////////////

_Tanjiro’s Diary_

_Day 109_

_Today’s the day. If everything goes right, you’ll be awake by tomorrow morning. I’m glad. I hope you can still read, otherwise this whole diary would have been pointless._

_See you soon._

…

Shinobu injected the last drops of the medicine into Nezuko. Her body shuddered from the foreign substance. He winced empathetically, feeling the syringe on his own arm. Nothing wrong, yet.

“If all goes well, she’ll be awake by next morning.” she estimated ”That way, there’s no chance for her to panic and run away. Just make sure no sunlight gets in and she’ll be fine.”

“Got it.”

“You sure you want to wait here?”

“If something happens, I want to be there to help her this time.” He smiled.

“Such a nice brother,” Shinobu smiled. “I’m going to bed. Call me if anything happens.”

Of course, he said. “Thank you, for everything.”

She stopped at the door. “My sister believed in demons,” She began, her face to the full moon overhead, her back to the room. “she thought that, since they used to be human, they could still regain their humanity. Even after everything she suffered, she still believed that there was hope for them to live a better life, for them to become better. For everyone.”

Tanjiro shared his thoughts “She must be nice.”

“She was.” The words weren’t spat with any praise or bitterness. Only remorse. “Goodnight, Tanjiiro. Good night, Nezuko. See you in the morning.” The door softly clicked into place.

Watching the moon crawl across the window, slowly dipping below the frame, the hours wore themselves on him little by little. It was horribly windy tonight. He shivered, like that night long ago. He wrapped himself in a blanket and waited, the cold still creeping up on him. At midnight, he was drunk with lethargy. He shouldn’t have exercised earlier; now his body was trying to pay for the spent energy.

One hour past midnight, he kept pinching his leg.

Two hours past midnight, his leg grew numb.

Three hours in, he resorted to slapping himself.

When the sun peeped it’s head over the horizon, he gave in for one, quick, nap.

…

_The demon’s tendrils crawled through every pore on his body. Every orifice, little crack was invaded by a bone-bristled tendril. When he spoke, the tendrils quivered, drilling deeper into Tanjiro’s body. The demon glanced at his family, his cat eyes darting to each sister, brother, and mother. With a silent command, the tendrils lashed out…_

…

He gasped, clutching his missing arm as if it was still there, the sun above the horizon. At least an hour had passed.

 _A demon slayer who can’t even stay awake at night. I need to be better._ He cursed.

At the opposite end of the room, at the opposite end of the bed, Nezuko stared at the curtain-covered window, her curious eyes following the few beams of permeated light. Tentatively, her fingers skimmed the beams. She winced. So close, yet so far.

She finally turned to Tanjiro.

The muzzle couldn’t hide her beaming smile.

**Notes for the Chapter:**

> Comment on what you thought about the chapter! Too long, too short, or any inconsistencies you noticed.


	7. Testaments of Tanjiro Part 2

**Notes for the Chapter:**

> Author's note:  
> No significant new spoilers.  
> Please enjoy the story.

////////////////////////////////////////////////////////////////////////////////////////////////////

“Say ‘ah.’”

Tentatively, the demon opened her mouth, ferally grunting ‘ah’ whilst-while. Her throat was clean, the doctor observed. Everything was as expected. She head-patted Nezuko and slid the bamboo muzzle back in place. Nezuko protested, but was ignored with a light slap to her wrist. “Oh please don’t take it off Nezuko. We don’t want those fangs to cut anything now do we?”

Tanjiro anxiously waited for her verdict. “Her condition is a bit weak, but it’s nothing that time and patience cannot fix.” Shinobu said.

“That’s great!” He hugged Nezuko for the fourth time that morning. She struggled to breathe against the one-armed embrace of brotherly love.

“Aww, how sweet.” Shinobu smiled. “Well, I’ll leave you two alone. I’ll be in my study if you need me.”

“Thank you, for everything.”

“Oh, I was only doing my job. Besides,” Her purple eyes grinned at Nezuko. “I’m still waiting on the results.” The demon gulped. “Okay! Bye!” She closed the door behind her.

“She’s scary.” He said when the Hashira’s footsteps had become faint whispers. Nezuko agreed. “How was your sleep? Good?”

She gave him two thumbs-up.

“That’s great! You can still sleep, but only during the day this time. That way you can be awake during the night. It’s an awkward schedule, but it balances everything out. It would be even better if we found something you could eat.”

She licked her lips at the thought of food.

“Do you know how long you were asleep?” She guessed with 5 fingers, for 5 days. Her eyes popped out of her head when he told her the truth. She flopped on her bed, the realization trickling through her.

“Weird right? And I thought Rokuta slept a lot,” he chortled. She vaguely remembered Rokuta – her youngest brother – and snickered, more due to Tanjiro’s hearty laugh than her own knowledge of the joke.

He wanted to ask her if she had any dreams about their family, but her current state made a clear answer impossible. He focused, instead, on the present.

“By the way, I wrote this.” He handed her his journal. “It’ll help you catch up on everything that’s happened since you fell asleep.” Eyes sharpened, brow narrowed, Nezuko read the first entry with undivided focus. Minutes later, she had yet to turn the page.

She had forgotten how to read.

She shoved the journal aside, moodily growling. He’d have to read it for her later. In spite of this, relief continued to wash over him. His sister was awake. For now, that was all that mattered.

////////////////////////////////////////

Nezuko followed her nocturnal schedule: sleeping during the day, rehabilitating during the night. Her Demon Slayer training had yet to start, which relieved and worried Tanjiro. While he didn’t want Nezuko to get into trouble, it would be great if she could protect herself.

Her rehabilitation, meanwhile, was spent entirely with Shinobu and her assistants.

Sumi, Naho, and Kiyo taught Nezuko basic manners: How to braid her hair, how to take a bath, brush her teeth, and change her clothes. The last skill was impossible to teach, as she refused to take off anything more than her usual attire. Only now did Tanjiro notice the happy pink kimono, despite having never been washed, smelled as fresh as the day it had been sewn. Likewise, the once ragged Haori looked brand-new, subsiding his initial worry of her favorite clothes tattering.

He asked Shinobu about it. “Oh her clothes? It’s a common habit amongst demons,” She explained. “the clothes they transformed with will also transform, becoming a pseudo second-skin for them. It even disintegrates with them when they die. Demons can change and assimilate new clothes, yet I rarely see one do so.” She shrugged. “Perhaps it's because of sentimentality.”

Shinobu, meanwhile, continued her experiments on Nezuko, using samples of her blood to test new drugs and poisons. She pouted when she discovered Nezuko’s regeneration was abysmal compared to typical demons'. Tanjiro made sure to watch her whenever she experimented on Nezuko.

As for Aoi, she had become Nezuko’s speech therapist, her trust in Shinobu outweighing her distrust in Nezuko. Tanjiro passed by one such lesson, one day, curious.

“What are you teaching her?” He piqued. Aoi was showing Nezuko hand signs from a book, correlating them to objects or phrases.

“Sign-language. Nezuko’s transformation caused her intelligence to degrade, she's like a human toddler now, so I decided to work within that framework. Sign language is easier and quicker for children to learn than talking, since it involve the hands and images, not complex vocal cords. She’s picking it up pretty quickly!” Aoi boasted, like a preschool teacher complimenting her golden star student. “Show him Nezuko!”

Nezuko placed her fingers on her forehead and saluted Tanjiro.

“That means ‘hello’”

Nezuko patted her chest and tapped her index fingers together.

“That means ‘my name is’, I’ll eventually teach her to sign her own name.”

Nezuko flicked her middle finger, a goofy grin darting across her face.

“And that’s…” He frowned.

“Nezuko!” The person in question snickered as Aoi’s face flustered an embarrassed red. She slapped her student, failing to stop her from snickering. “No!”

“I can’t believe you taught her that.” _What would mom say?_

“I didn’t teach it to her! Not…directly. There was this rude patient I was dealing with, Nezuko was watching from the door and…” Aoi's shoulders conceited. “Like I said, she’s a quick learner. I promise, that is the only insult she knows and will ever know.” Behind her, Nezuko doubtfully shook her head.

“Right…”

He later borrowed a copy of the book, memorizing all the hand signs in it.

////////////////////////////////////////

Eventually the Doom Slayer returned, a new gun at his side. It was a rusty shade of brown, narrower than his combat shotgun, with a chain cartridge that fed a buffet of bullets into the hungry gun. _It’s bigger than the other gifts._ He noted _._ The Doom Slayer cashed in his normal delivery of screaming heads and silently asked for an update.

VEGA replayed the mysterious message, each syllable uttered with dried, cold compassion. The voice hit Tanjiro like a bucket of cold water, chilling him to his core. It was the voice of a man whose ambitions had no budget. Wisty hissed at the voice. The recording ended.

Having grown used to the Slayer’s habits, neither Shinobu nor Tanjiro questioned him. They waited, instead, for his reaction. It was surprisingly severe for such a short message:

Veins thickened, particularly the ones on his forehead - swelling like ugly pimples. Feet shifted impatiently. His ironclad grip about his gun castened, wishing it had interdimensional range.

He quickly composed himself, deciding that his rage would be better saved for later. Quietly, he left the room.

“Please make sure he doesn’t destroy anything.” Shinobu whispered. He nodded and followed him. Perhaps the Doom Slayer had less friends than Tanjiro had originally thought.

He was heading for Nezuko’s room. First, though, he passed by the three young assistants.

“Hi Mr. Doom Slayer!” they paused their game of jump rope. “Can we play with Wisty?”

“Please?” Sumi pleaded.

“Please?” Naho echoed.

He obliged, the lazy fluffball purring as the three children showered him with hugs, pets, and squeals.

He reached Nezuko’s room.

“I know I’ve said this before, but could you please knock first?” He didn’t. Exasperated, Tanjiro slid in after him.

Nezuko was asleep. He feared, for a horrible moment, that the past few weeks had been a lucid dream. Then her body yawned beneath the blanket, Tanjiro smiled. 

Nezuko groggily crawled out of her woolen cave, still dressed in her pink kimono. She licked her lips hungrily, as she did when woken up early, and rubbed the afternoon dust out of her eyes. She hadn’t noticed the two invaders. At first. She rubbed her eyes again; a look of indignity dawned upon them.

She shrieked and threw a pillow at the Doom Slayer, bouncing off of his helmet.

“I told you to knock,” He sighed as Nezuko complimented her attack with an Aoi-taught middle-finger. “Shinobu was able to wake her up while you were gone. She still sleeps a lot, but we can wake her up normally now. She's become more active, especially during the night. By next week, she’ll start her training. It’s exciting.”

Neither Nezuko nor The Doom Slayer jubilated at this, both glaringly fixated at the other. Nezuko snarled at the Doom Slayer. He – in his scornful, silent way – growled back.

“guys…” _heck heck heck heck heck heck heck heck heck heck heck heck heck heck heck heck heck heck heck heck heck heck heck heck heck heck heck heck_ He jumped between them. “It was a misunderstanding, Nezuko. He thought you were still out. Let us all just calm down, breathe, and relax.”

Nezuko grumbled as she snuggled back into bed, still flipping the Doom Slayer the bird.

The Doom Slayer didn’t have time for this. He slammed the door behind him, the innocent wood crying from the force. Months ago, Tanjiro’s skin would have crawled from such a close call. Now? He breathed a soft sigh of relief. _I’m getting too used to this,_ he groaned.

////////////////////////////////////////

The sun sank below the horizon; the opportunities of the night rose with it. Tanjiro fiddled with his sword, waiting. Sumi hopped over to him. “Okay! Shinobu said she’s ready!” It was time.

“Thank you Sumi,” Tanjiro knocked on the door. “Nezuko, it’s time to go.”

Shyly, the door creaked open. Nezuko was dressed in her usual attire, with the exception of a practice sword and belt – identical to Tanjiro’s own in design but smaller in size – fitted around her waist.

“Nice. Make sure you don’t bump it against anything. Trust me, easy mistake.” He advised.

 _Got it,_ she signed, her hands moving with confidence.

“Wow! You’re getting better at that!” Nezuko blushed, but the comment was well-deserved. She could now sign basic sentences and names with ease. She still had trouble speaking, but Tanjiro was sure they’d get there eventually. Baby steps.

With her hand in his, they left the Butterfly Estate. They passed by several Kakushi along the way, an injured Slayer slung between them.

He tried to look elsewhere, but his eyes couldn’t resist glimpsing at the victim’s twisted legs, his missing fingers, trembling eyes. Nezuko’s grip around Tanjiro’s tightened.

 _That could happen to me and Nezuko one day. That did happen to me and Nezuko._ He winced, the past crawling out of the dark, forgotten corner of his mind. He bit his lip and carried on.

Unlike Tanjiro, Nezuko’s training would have to be more private. It needed a secluded space with lots of shade, a good bed, and be easy to access.

A mile and a little more away, there was a single-storied summer home, large enough to house at least four people, sturdy enough to bear most harsh weather. A river flowed calmly behind the house. Pillaring trees surrounded the opposite side of the abode, clearing semi-circularly at the house’s entrance. The summer home was a part of Shinobu’s inheritance, but her duties and its uses had never aligned. Until now.

A great Black Pine tree stood near the summer home - the tallest tree around, towering over it’s barked brethren like a friendly giant. Shinobu was relaxing beneath it’s welcoming shadow, wistfully staring at the tree. She soon noticed them.

“Oh my, you look so nice Nezuko!” The Butterfly Hashira beamed. It was, after all, the night she had been waiting months for. Tanjiro could emphasize.

 _I wear this everyday,_ Nezuko signed back.

Shinobu winced. “Well, you look especially good tonight!”

“Now,” she began, “there are numerous breath styles to learn, each with their own training regiments, techniques, and challenges. I will be teaching you the Breath of Flower. However, there’s something I want to test first.” Hanging from the highest branch of the tallest tree, a white-silk banner flowered in the wind, embroidered with lavender hem patterns.

“The test is simple: Cut the banner in half.”

 _That’s all?_ Tanjiro was shocked. Likewise, Nezuko questioned the Hashira’s decision making with a frown.

“I’m not finished: You have to cut it while it’s falling. Kanao?” Kanao poised next to the banner, her butterfly hair clip glittering in the moonlight. He swore she wasn’t there a minute ago. “Perfect. On my mark, cut the string.” She bowed to her master. 

“Now, let us see that demonic strength of yours,” Shinobu taunted.

Nezuko glared at the smiling Hashira. This test felt more like a dare. With an odd sense of pride, she flimsily drew her blade and tossed the sheathe aside. Purple eyes drilled into Nezuko’s skin. Red eyes too – all eyes in the woods curiously watched her.

Shinobu snapped her fingers.

The banner fluttered towards the ground – light as a feather, blissfully swaying with the wind.

Nezuko raced up the tree with demonic speed, blade in hand. Once in position, she leapt, swinging at the banner with all her might.

The sword slipped out of her grasp. She crashed to the ground.

She missed, the banner still fluttering to the ground intact.

Hastily she grabbed the sword and tried again, tightening her grip.

The banner flowed over her blade as if it, too, were but thin air.

Another miss. She tumbled to the ground in defeat.

The banner touched the ground, but she wasn’t done yet. She threw the little thing into the air and struck.

Another miss.

It didn’t take long before Nezuko looked like she was trying (and failing) to swat a fly with her sword. Eventually she surrendered to the ground, ripping off her muzzle, panting.

“Oh my,” Shinobu frowned. “Is someone tired? Do you need another nap Nezko?” Nezuko glowered at her. “What a fierce face! If it makes you feel any better, you’re supposed to do this _after_ you’ve learned all the Breath of Flower techniques. I was simply feeding my curiosity.” Shinobu plucked the banner off the ground, passing the fine silk between her fingers.

“This is why, despite all your strengths, you demons can still be beaten. Without proper finesse,” Shinobu tossed the banner into the air. Her blade pierced the banner, cutting right through the hem’s pistil. “Strength is useless.” The petite woman towered over Nezuko.

“Now then,” she grinned. “Let us begin.”

////////////////////////////////////////

Nezuko’s training dragged on throughout the night, dawn forcing her to sleep at the summer house.

“That was…something.” Shinobu didn’t try to hide her disappointment. “I wasn’t expecting anything grand. Honest. I also didn’t expect to spend most of the night teaching her basic sword etiquette. And her grip,” Her lips cringed. The right words were too sour to utter.

“Was it that bad?” Tanjiro recalled his first time with a sword. While inexperienced, he had quickly gotten used to the tool. It was similar to an axe, albeit longer and not used against wood. Nezuko, on the other hand, had a salmon’s grip and a boar’s delicacy with her blade. Perhaps her inexperience with hard labor made the sword all the more strange to her, or maybe she was used to using finer tools, like sewing needles. Whatever the cause, the effects were clear.

“It’s not encouraging. Maybe there’s a reason why most demons don’t learn Breath Techniques.” She sighed. “Time for some more trial and error.”

“Mostly error” Tanjiro jested.

////////////////////////////////////////

Little progress was made in the nights to follow. Stumbling, tripping, Nezuko tried her best to little fruition. The struggle showed a completely different side of Nezuko: She would kick rocks, growl, sulk, and even throw her weapon in fits of rage, wasting precious time. The tantrums were new to him. When she was a human, Nezuko usually laughed everything off. It seemed her transformation had amplified everything about her. Not only her strength and vitality, but her emotions as well.

The news didn’t get any better.

One day, training by the gate, Tanjiro saw two decorated Hashira arrive. He could tell their status from the poignant demon blood that defiled their weapons.

The woman had a gracious bosom, emphasized by her unbuttoned uniform. A white Haori flowed behind her. The man accompanying her wore the same uniform (albeit more modestly) and unlike the woman had black, not watermelon, color hair. A snake playfully slithered around his shoulders.

From the way he walked next to the woman, as well as his shorter height, he reminded Tanjiro of a dog following his owner.

“Hi!” Tanjiro waved.

“Shut the hell up you suckling cunt, wasting everyone’s resources.” He barked.

“Sorry, he gets like this sometimes,” The woman apologized.

“It’s fine,” _That really hurt though._ Tanjiro mentally sobbed. The Hashira’s continued on to Shinobu’s study.

Curious, Tanjiro followed them. Shinobu usually kept her window open. He could eavesdrop on them there. Of course that would be a very rude thing to do.

 _Well, it’s not really eavesdropping if I’m only training, right?_ So he trained as hard as he could, as softly as he could, so he could eavesdrop on the conversation he was not eavesdropping.

 _It’s not eavesdropping if I’m training._ He repeated. _It’s not eavesdropping if I’m training..._

“Mitsuru!” He heard Shinobu shriek.

“Shinobu!” The two girls hugged each other. Only when Mitsuru encouraged him did Obanai join their embrace.

“What brings you two here?” She asked.

“The usual: Recipes, gossip, the like. Obanai came ‘cause he wanted hang out with you too!”

“I bet he did,” Obanai glared at Shinobu’s smirk.

“So, quick question, are you coming to the Hashira meeting this week?” Mitsuru asked.

“Oh my, the meeting, I almost forgot! I’ll come, but I can’t stay for long. Busy schedule, sorry!”

“It’s pretty quiet around here, dunno why you’d be so busy.” Mitsuru wondered aloud. ”There’s something else I wanted to mention. Last thing, I promise: We’ve been getting weird reports from the scouts lately. It’s about the demons.”

Shinobu paused. “Yes?” Her ears quivered, all too curious.

“Scouts have been finding demon corpses. Not the usual remains, like weapons or gear, but actual demon corpses.” The words shuddered throughout the room, stiffening everything to an abrupt halt.

“They didn’t disintegrate?” Shinobu whispered.

“No. According to reports, they had been petrified into still statues, with faces like this:” Mitsuru’s mouth and eyes shrieked, as if her soul was being sucked through her face. “hmm…I don’t know if I’m doing it right. You try Obanai.”

“No.” The snake Hashira snapped.

“Pretty please?”

“…” Reluctantly, but willingly, Obanai’s face mimicked a soundless scream.

“Perfect!” She giggled. “They looked just like that.”

“Odd.” Shinobu pursed her lips. “Could you bring me one to study?”

“We’ll try, but I heard these corpses are really fragile, like one big sandcastle made out of ash. No reports of an intact body yet. Plus, I heard they smell really, really bad. No biggie,” she perked. “If anything, we should take this as a good thing. If this is only happening to demons, it means someone is out there helping us!”

“Perhaps.” Shinobu didn’t sound as assured.

“We can figure it out later. Right now, we have more important matters at hand. So I was passing by this town and heard that…” Mitsuru launched into a lengthy stream of new foods and gossip she had learned, leaving Tanjiro to ponder the news.

 _Could it be the Doom Slayer’s work?_ He doubted it. It was not in his nature to leave any demon standing, and he had never done something like this before. But, then, who could it be?

////////////////////////////////////////

“Your thumb is off. Start from the beginning.” Shinobu instructed. “Another 300 strikes.”

 _I’m already strong, why do I have to do this?_ Nezuko signed with numbed fingers.

Originally, Shinobu had skipped straight to the techniques, believing Nezuko already had supple strength. When that hadn’t worked out, she peddled back to the reliable basics. Suffice to say, this pissed off Nezuko. A lot.

“Practice makes perfect Nezuko. Now, please do it again.”

Teeth clenched, Nezuko took her stance. _1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,10-_ The blade slipped out of her grasp. Again. Her fingers had a mind of their own, loosening the moment Nezuko got distracted.

“Oh my. Well, you know the drill. From the beginning.” Shinobu sighed. 

Nezuko finally snapped. She threw her sword into the dirt, stomping away at it until it cracked. It’s metallic cry echoed throughout the forest.

“What happened?” Tanjiro had been training in the woods, alarmed by the sharp noise. What alarmed him even more now was the inferno raging in Shinobu’s eyes. With little warning, she kicked Nezuko in the face, her jaw cracking like her blade. “NEZUKO!”

“…” Shinobu inspected her sandals. She wiped the blood off of them with a handkerchief and regained composure. “I’m sorry, Nezuko. We will stop for tonight. We all need some time to think.” She whispered.

Nezuko was stunned. _But the sun hasn’t risen yet._ She signed.

“Well, If you cannot respect your sword, you clearly cannot respect my guidance.”

_But-_

“We’ll start again once you’ve calmed down.” She politely spat. The light of the moon shined on her daintiness, her scorned face, highlighting the disappointment in her eyes. The Butterfly Hashira fluttered into the woods, returning to the Butterfly Estate.

“Nezuko, are you okay?” She hadn’t moved an inch, Her muscles stiff to the touch. Her jaw sluggishly clicked back into place.

 _Please go._ Her hands were shaking. From shame? From spite? Perhaps both. Only because of her insistence did he finally leave her alone, pretending to leave but instead hiding behind a tree. _Hopefully she doesn't do something bad._

Thinking he was gone, Nezuko walked up to the tallest pine, it’s height a testament to the care it once enjoyed. She kicked it.

Over and over, the black pine rang like a wooden bell.

He waited until Nezuko tired herself out, until her head was caked in sweat and her foot was a bloody mess. She sulked into the house, clutching her broken foot. It was almost dawn by then. _She really is a different person now._

////////////////////////////////////////

The lethargic embraces of his pillow cuddled him, yet he couldn’t sleep, the previous night gnawing at him like midnight flies.

They had been here for six months. One hundred and eighty days. While his physique had improved immensely – one handed push ups now a past struggle - he had yet to learn a breath art. Nezuko was showing little signs of improvement, and something was happening to the demons. Something that could change everything.

And here he was, unable to do anything about any of it.

He was lost in thought. So lost, in fact, that he didn’t notice someone else was in his room. Not until he tapped his shoulder.

“Hello.” Greeted Giyu Tomioka.

Too shocked to move, too bewildered to react, Tanjiro forced himself to whisper. “Um…Hi. Giyu Tomioka, right?”

“Yes.”

“I didn’t hear you knock.”

“Because I didn’t.”

“Right. Of course.”

“…”

“…”

He was confused. “Do you need something? If you’re looking for Shinobu, she’s not here at the moment.” _She’s training Nezuko now,_ he remembered, _I wonder how that’s going._

“Actually, I came to see you.” Tanjiro focused on his nose, trying to see if he could smell his true intentions. He noticed something interesting: Whereas Shinobu was coated in a dense perfume smell, occasionally mixed with intense spikes of anger, Gyu’s scent was like an ocean breeze, calm and placid. They were opposites, Tanjiro realized, in the same way intensity was the opposite of apathy. Likewise, Giyu's words were genuine.

“About what?” Tanjiro replied.

Giyu saved his answer for later. “Is it okay if I sit by you?” He asked first.

“Sure.” Tanjiro petted the space next to him. Giyu filled it up, his brow knitted deep in thought. Like the coming of high tide, he began slowly.

“Shinobu told me what happened to your family, how they were all devoured by a demon. I was supposed to be there to stop that demon, but I was forced to retreat. Not only was I humiliated, I failed to save someone from the demons’ wrath. Again.” He confessed, his eyes staring at Tanjiro’s scar-ridden chest; his missing right arm. “My ineptitude has ruined you and your family. I am sorry.”

“You’re blaming yourself?” Tanjiro shook his head. “You’re not the one who killed them. You did what you could. There's no need to apologize.” Giyu’s ocean eyes shined otherwise.

“Do you miss them, your family?” He asked.

“…” Tanjiro couldn’t put it into words. He _hadn’t_ put it into words for the past few months. Even when he had written about his family to Nezuko, it had felt fictitious. Every time he thought about them, he wanted to think _Mom is nice,_ not _Mom was nice_ ; _Rokuta is cute,_ not _Rokuta was cute._ The less he talked about them, the more distant their deaths felt. Words weren’t spoken without reason; silence its repression.

Yet he never wanted to forget them, from the moment he first saw them, to the last moment he hugged them. Their existence was a puzzle, each moment with them was a necessary piece. When everything was in place, his family was still gone, but they were not far or faint. They were real.

Tears trickled. He clutched his wistful, aching heart. He missed that feeling. “Yes. I miss them a lot. They were everything to me. I can’t deny it.” Giyu sulked. “They didn’t die peaceful deaths, and I wish I could have done more to help them then, but I couldn’t. And now I can’t. It’s in the past now.”

“But I don’t regret the time I spent with them, loving them. Knowing them, they wouldn’t want me to lament their deaths. They would want me to push forward for a better future. A future where their lives weren’t wasted. That is why I want to become a demon slayer, to fight for a better future where everyone can be happy. Through me, my family will live the lives they deserved.”

Giyu nodded. “And what about your sister?”

“Huh?”

“Your dead sister. Shinobu told me her death was especially painful. Would she wish the same things for you?”

 _Right. Lying._ “Yes. Even my…dead sister.” His face crumpled like shabby origami (he could never lie with a straight face).

“Are you okay?” Giyu frowned.

“I…have to sneeze…because…I’m so sad.” His origami crumpled. “Achoo.”

“Bless you.”

“Thanks.” **SPEECH 100**

After a moment of silent reflection, Giyu continued. “I came here to make a proposition. There is a retired Water Hashira known as Urokodaki. He can teach you the Breath of Water style.”

He gasped. This was the opportunity he had been waiting for, the chance to become a demon slayer. His chance to avenge his family and all those who had been slain, to secure a future free of the demons’ wrath. This was his chance to push forward.

So why did he feel so unsure?

“Do I have to decide now?”

Giyu shook his head. “Whenever you are ready, travel to Satori mountain. Your training will begin there. Once it does, I advise you stay there until the end of your training. Unbroken focus is a key aspect of any discipline.” He stood, his ocean eyes glaring into Tanjiro’s own crimson eyes. “It is your choice.”

With nothing left to say. Giyu closed the door behind him.

Again, the lethargic embraces of his pillow cuddled him. Again, Tanjiro couldn’t sleep.

There was nothing else to be gained at the Butterfly Estate, nothing would be lost if he left. Except, Nezuko. Even if he somehow managed to bring her with him, if he somehow managed to hide her from Urokodaki, she wouldn’t get her training. And if anything happened to her, say an illness or weird mutation, what could he do?

The way he saw it, he had two options: One was difficult, the other was unproductive. He knew which was the best option, but it didn’t make him feel any better.

He dozed off, his mind having worried itself to shreds.

////////////////////////////////////////

_Tanjiro’s diary_

_Day 182_

_Nezuko, I’m leaving the Butterfly Estate to learn from a former Hashira. He’s a kind old man called Urokodaki. If I train with him, I can learn the Breath of Water style._

_I don’t like this. We’re the only Kamado’s left in the world, the only family either of us have right now is each other. I don’t want us to get separated, but this is an opportunity I can’t afford to miss out on. I already talked with Shinobu about this. Everyone at the Butterfly Estate will help you with whatever you need, and I’ll come back right after I’m done training._

_I promise, after the training and exams, we will work together to find a cure for you. But for now, I have to go. Please keep training hard Nezuko, and stay safe._

_Let’s push onto the future, together._

_Prayers,_

_Tanjiro_

////////////////////////////////////////

He had packed everything he needed: Sword, clothes, food, a map. He would wait until it was nighttime, until Nezuko was awake, and then read his goodbye to her and leave. He had a lot more to say to a lot more people, and it wasn’t the best goodbye, but he didn’t want to save any time for second thoughts. The sun was just settling below the horizon.

Shinobu had already bid him safe travels.

He sighed. Hopefully Nezuko would take it in good taste.

Someone knocked on his door. Tanjiro opened it.

It was the Doom Slayer.

“Oh, hello. Did you already meet Shinobu?”

Silence.

“Great.” Amidst the hectic month, he’d forgotten to say anything to the Doom Slayer. Now would be his only chance. “I’m leaving tonight.” He blurted. “I’m going to train to become a proper Demon Slayer. I really appreciate everything you’ve done, even if it was only in your best interest, but I can’t keep living off of others’ generosity. I want...I want to change the world with my own hand. I don’t want all the help I’ve gotten to be wasted. And...” He took a deep breath. 

“Please, please don’t kill my sister. Even if she goes feral, please try to help her.” he begged. “I promise if she does actually...really...kill... someone, I’ll take full responsibility.” His lips trembled. “And kill myself."

Silence.

He gave his pistol back. “I never got the chance to return this.” The Doom Slayer stared at it. Reluctantly, he pocketed the weapon.

“So, thank you, for everything. And good luck finding him.” Tanjiro closed the door.

////////////////////////////////////////

She slammed her foot into the tree, the great pine shivering to its very tips. She kicked it again, and again, and again, and again, her frustration only worsening each time.

 _Fuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckshitfuck,_ she silently screamed.

A month of work and for what? Because of her ineptitude, he had left. She knew that to be the bitter truth.

CRUNCH. She clutched her now-broken foo - a mangled mess of muscle and bone. No matter. It would heal soon, unlike her older brother. His wounds would only get worse and worse.

She winced as her foot slowly mended itself. By demon standards she was pathetic, by human standards she was clumsy. Yet, everyone seemed to care for her regardless. Because she was unique.

 _I don’t deserve this,_ she crumbled. _I don’t deserve such kindness._

“Oh my, that must hurt.” Nezuko jumped out of her skin. She was alone; the familiar voice suggested otherwise. Oddly enough, it had sounded like an older Shinobu. Her eyes searched for the mysterious speaker.

A hem flower fluttered in the wind, landing on her head. She looked up.

Legs swaying, fingers laced, a slender woman watched her earnestly atop the highest branch of the tallest tree. Like her voice, she bore a similar yet older resemblance to Shinobu: she wore the same butterfly haori, the same gold-buttoned uniform, and a butterfly hair clip resembling Kocho’s own. There were differences, however: The woman’s eyes were softer in color, and her hair was longer, billowing to her waist.

“Sorry, I didn’t mean to interrupt you.” she flustered softly. “Please, finish your business first.” Nezuko couldn’t, consumed by surprise and curiosity.

 _Is she safe?_ Nezuko had never met her before. _Could she be another Demon Slayer?_ She tried to ask, but her throat was uncooperative. _Right. Talking. Still working on that._ Luckily, her expression told the woman all she needed to know.

She gasped. “Oh! My apologies, I forgot to introduce myself! I haven’t talked to anyone in a while, it completely slipped my mind!” Like a ghost of the night, the woman glided down the tree. She held out her hand to Nezuko.

“My name is Kocho Kanae, nice to meet you!”

////////////////////////////////////////////////////////////////////////////////////////////////////

**Notes for the Chapter:**

> Author's note:  
> Please feel free to comment your thoughts on the chapter. Too long? Too short? Cringy? I hope to improve with each chapter.  
> Also I'll admit, I was weak: Nezuko was doing American Sign Language (ASL) not Japanese Sign Language (JSL).


End file.
